Method and system for separating naphthalene aromatic hydrocarbon in complex system by combining separator azeotropic distillation and extraction

Abstract

The invention discloses a method and a system for separating naphthalene aromatic hydrocarbon in a complex system by combining separator azeotropic distillation and extraction, and the method comprises the following steps: introducing raw materials including a target product into a separator azeotropic distillation tower; a raw material and an entrainer are azeotropic and separated in the partition plate azeotropic rectifying tower to obtain a light component, an azeotropic component, an intermediate component and a heavy component, and the entrainer and a target product form a low-boiling-point azeotrope component which is output from the partition plate azeotropic rectifying tower; performing phase separation on the azeotropic component through a phase separator to obtain an entrainer phase and an oil phase, returning the entrainer phase to the partition plate azeotropic rectifying tower for cyclic utilization, and performing extraction and separation on the oil phase to obtain the target product naphthalene aromatic hydrocarbon. The entrainer is a compound composition composed of 1, 3-propylene glycol, ethylene glycol, ethanolamine and water. The method provided by the invention can be used for treating raw materials with complex components, and has better universality.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical engineering, and particularly relates to a method and system for separating naphthalene-based aromatic hydrocarbons in a complex system by combining partition azeotropic distillation and extraction. Background Art

[0002] Catalytic diesel and light cycle oil are rich in bicyclic and polycyclic aromatic hydrocarbons. Among the bicyclic aromatic hydrocarbons, α-methylnaphthalene, β-methylnaphthalene, 2,6-dimethylnaphthalene, 2,7-dimethylnaphthalene, 1,5- and 1,6-dimethylnaphthalene, etc. are important fine chemical raw materials. Among them, α-methylnaphthalene is an important monomer for producing polyvinyl chloride fiber and polyester fiber, β-methylnaphthalene can be used as an effective ingredient in biomedicine, 2,6-dimethylnaphthalene is an important monomer for high-performance new materials such as PEN, PBN, liquid crystal polymer (LCP) and polyurethane resin, 1,5- and 1,6-dimethylnaphthalene can be isomerized into 2,6-dimethylnaphthalene, and 2,7-dimethylnaphthalene is an important monomer for new materials. The components in catalytic diesel or light cycle oil are complex, including alkanes, cycloalkanes, monocyclic aromatic hydrocarbons, bicyclic and polycyclic aromatic hydrocarbons, etc. The content of bicyclic aromatic hydrocarbons is about 32-37%, including about 10-12% of methylnaphthalene and about 9-13% of dimethylnaphthalene. Extracting this part of naphthalene-based aromatic hydrocarbons can be used as an important raw material for fine chemicals and new material monomers. At the same time, the remaining light components and heavy components can also be used as blending oils. Due to the complex components of catalytic diesel and the relatively low content of bicyclic aromatic hydrocarbons, the extraction process is difficult and energy-consuming, and this part of high-value-added components has not been reasonably utilized.

[0003] According to the different boiling points of each component in catalytic diesel, the fractions can be roughly divided into light components, intermediate components, and heavy components. Compared with the BTX-rich mixture commonly used in aromatics extraction, the initial content of bicyclic aromatic hydrocarbons in catalytic diesel is relatively low. If direct extraction or extractive distillation processes are used, there are a large number of non-target products such as alkanes, cycloalkanes, and monocyclic aromatic hydrocarbons, resulting in a large amount of extractant consumption and a large logistics circulation volume, causing problems of high cost and high energy consumption. Using an additional pre-fractionation process for pretreatment often requires the use of 3 or more distillation columns.

[0004] The boiling points of commonly used sulfone compounds, pyrrolidone compounds, and amide compounds in the aromatics extraction process are close to the boiling points of the target product bicyclic aromatic hydrocarbons. For the extraction phase generated after using the extraction or extractive distillation process, the theoretical number of plates of the solvent recovery column using the traditional distillation method is relatively high, and it is difficult to separate and recover a high-purity recovered extractant.

[0005] Chinese Patent CN111954654A discloses a method for separating aromatic hydrocarbons by combining extractive distillation and extraction. The first tower is an extractive distillation tower, the second tower is an extraction tower, and the third tower is a solvent recovery tower. The unextracted benzene in the raffinate at the top of the extractive distillation tower enters the extraction tower for full recovery, and then the solvent is recovered through the solvent recovery tower. However, this method is mainly applicable to systems with a relatively high aromatic hydrocarbon content in the raw material (aromatic hydrocarbon content is 60-98% by mass, preferably 70-98%), and the main effective components extracted are light aromatic hydrocarbons (benzene, toluene, xylene). Therefore, the selection of extractants is mainly sulfolane and polyols for light aromatic hydrocarbons.

[0006] Chinese Patent CN110393940A discloses a method using a dividing wall column as an aromatic hydrocarbon extractive distillation device, integrating aromatic hydrocarbon extraction / extractive distillation and solvent recovery into one tower. The upper part of the extractive distillation tower is connected to an aromatic hydrocarbon condenser, the lower part is connected to a reboiler and a heat exchanger, and the bottom is connected to a solvent regenerator, a solvent condenser and a collector. However, it mainly describes the main connection structure of the device, and does not explain the composition of the system to be processed, the feed content, and the extraction effect that can be achieved after passing through the device. It also does not explain the number of theoretical plates, the feed plate position, the draw plate position, and the dividing wall position of the dividing wall column used.

[0007] Chinese Patents CN202011077806.2 and CN201910947924.5 disclose a method for separating by extraction with deep eutectic solvents. The deep eutectic solvents contain a hydrogen bond acceptor and a hydrogen bond donor. The hydrogen bond acceptor is mainly one or more halides, and the hydrogen bond donor is one or more weak acids, polyols, esters. At the same time, a Lewis acid salt is also added. However, this method is applicable to application scenarios where the non-aromatic content in the raw material is relatively low and the total content of aromatic hydrocarbons (monocyclic aromatic hydrocarbons + polycyclic aromatic hydrocarbons) is relatively high. The extractants used focus on the separation of monocyclic aromatic hydrocarbons and polycyclic aromatic hydrocarbons, rather than the separation of non-aromatics and aromatic hydrocarbons.

[0008] Chinese Patents CN202110658326.3 and CN202111126760.3 disclose a method for extracting polycyclic aromatic hydrocarbons from catalytic diesel by using ionic liquids through a multi-stage countercurrent-crossflow combined extraction technology. The raw material and the solvent pass through two extraction towers, namely the first stage and the second stage. Non-aromatic hydrocarbons are obtained at the top of the flash tank S1, and aromatic hydrocarbons are obtained at the top of the flash tank S2. The solvent recovered at the bottom of S1 and S2 is recycled back to the extraction tower. However, the extractant used in this method is a mixed ionic liquid, and the recovery of ionic liquids is relatively difficult and it is easily contaminated and difficult to be recycled. Therefore, it is suitable for treating some high-value-added and simple-component systems, and is not applicable to catalytic diesel with complex components. In this technology, the targeted substances are model compounds containing only two components, and the real components of catalytic diesel often contain more than a dozen components. The applicability of this method to real components is not demonstrated.

[0009] Chinese Patent CN115992013A discloses a method and system for separating mixed dimethylnaphthalene from mineral oil, and provides a system for separating mixed dimethylnaphthalene from mineral oil, including: an extraction unit, a distillation separation unit, and a solvent purification unit. The distillation separation unit includes a first distillation column and a second distillation column, and the solvent purification unit includes a back-extraction column 4. However, the raw materials used in this method and system must be the 250-280°C narrow distillation fraction after rectification and splitting, and cannot directly process diesel raw materials; and the extraction agent used is an ionic liquid type extraction agent, which is relatively expensive. Summary of the Invention

[0010] The object of the present invention is to provide a method combining partition azeotropic distillation and extraction for separating naphthalene-based aromatics in a complex system. The initial enrichment section of this process uses the partition azeotropic distillation process to separate light components, azeotropic components, intermediate components, and heavy components in a single column. The separation of the azeotropic component and the intermediate component is achieved by forming a low-boiling azeotrope with the azeotropic agent and the target products (methylnaphthalene and dimethylnaphthalene), thereby realizing the separation from alkanes and alkylbenzenes with components having similar boiling points. The present invention can solve the problem of low-content raw material feeding that cannot be processed by single extraction or extractive distillation processes; compared with the process with an initial enrichment section, it solves the problem that 3-4 towers are required in the traditional process, and the energy consumption and equipment investment are relatively high; the extraction concentration section combines the process of an efficient extraction agent and the back-extraction method to solve the problems of difficult extraction agent recovery and high energy consumption.

[0011] To achieve the above object, the present invention provides a method for separating naphthalene-based aromatics in a complex system by combining partition azeotropic distillation and extraction, and this method includes the following steps:

[0012] Introduce the raw material containing the target product into the partition azeotropic distillation column, and the raw material and the azeotropic agent azeotropically distill and separate in the partition azeotropic distillation column to obtain light components, azeotropic components, intermediate components, and heavy components. The azeotropic agent forms a low-boiling azeotrope component with the target product and outputs the partition azeotropic distillation column; the azeotropic component is phase-separated by a phase separator to obtain an azeotropic agent phase and an oil phase. The azeotropic agent phase returns to the partition azeotropic distillation column for recycling, and the oil phase undergoes extraction and separation to obtain the target product naphthalene-based aromatics;

[0013] The azeotropic agent is a compound composition composed of 1,3-propanediol, ethylene glycol, ethanolamine, and water.

[0014] In the method for separating naphthalene-based aromatics in a complex system by combining partition azeotropic distillation and extraction of the present invention, the mass ratios of 1,3-propanediol, ethylene glycol, ethanolamine, and water in the azeotropic agent are: 1,3-propanediol 40-80%, ethylene glycol 10-40%, ethanolamine 5-30%, and water 5-10%.

[0015] The method for separating naphthalene aromatic hydrocarbons in a complex system by combining dividing-wall azeotropic distillation and extraction according to the present invention, wherein a raw material containing a target product is introduced into the middle of a dividing-wall azeotropic distillation column, a dividing wall is provided in the dividing-wall azeotropic distillation column, and an azeotropic agent is introduced from below the dividing wall; the separated light components are output from one side of the top of the dividing-wall azeotropic distillation column; the azeotropic components are output from the other side of the top of the dividing-wall azeotropic distillation column; the separated intermediate components are output from the middle of the dividing-wall azeotropic distillation column; and the separated heavy components are output from the bottom of the dividing-wall azeotropic distillation column.

[0016] The method for separating naphthalene aromatic hydrocarbons in a complex system by combining dividing-wall azeotropic distillation and extraction according to the present invention, wherein the extraction comprises the following steps:

[0017] The oil phase is input into the lower part of an extraction column, an extractant is input from the upper part of the extraction column, and the extractant in the upper part of the extraction column and the oil phase input from the lower part of the extraction column undergo a multi-stage countercurrent liquid-liquid extraction process to separate the aromatic hydrocarbons and non-aromatics in the oil phase, and a component rich in alkanes is obtained at the top of the extraction column, and an extraction phase rich in aromatic hydrocarbons and the extractant is obtained at the bottom of the extraction column;

[0018] The separation comprises the following steps:

[0019] The extraction phase is input into a solvent recovery column for separation, a recovered extractant is obtained at the top of the solvent recovery column, the recovered extractant is input into the upper part of the extraction column for recycling, and the target product naphthalene aromatic hydrocarbons are obtained at the bottom of the solvent recovery column.

[0020] The method for separating naphthalene aromatic hydrocarbons in a complex system by combining dividing-wall azeotropic distillation and extraction according to the present invention, wherein the separation further comprises a back-extraction process, which specifically comprises the following steps:

[0021] The extraction phase is input into the lower part of the back-extraction column, a back-extractant is input from the upper part of the back-extraction column, and through a multi-stage countercurrent liquid-liquid back-extraction process, the extractant and aromatic hydrocarbons in the extraction phase are separated, and the target product naphthalene aromatic hydrocarbons are obtained at the top of the back-extraction column, and a back-extraction phase mixed with the extractant is obtained at the bottom of the back-extraction column;

[0022] The back-extraction phase is input into a solvent recovery column for separation, a recovered back-extractant is obtained at the top of the solvent recovery column, the recovered back-extractant is input into the upper part of the back-extraction column for recycling, a recovered extractant is obtained at the bottom of the solvent recovery column, and the recovered extractant is input into the upper part of the extraction column for recycling.

[0023] The method for separating naphthalene aromatic hydrocarbons in a complex system by combining dividing-wall azeotropic distillation and extraction according to the present invention, wherein the extractant has the property of being affinity for aromatic hydrocarbons, and the extractant is selected from at least one of furfural, sulfolane, dimethyl sulfoxide (DMSO), and N, N-dimethylformamide (DMF).

[0024] The method for separating naphthalene aromatic hydrocarbons in a complex system by combining dividing wall azeotropic distillation and extraction of the present invention, wherein the mass ratio of the extractant to the feed stream of the extraction column is 2-4:1.

[0025] The method for separating naphthalene aromatic hydrocarbons in a complex system by combining dividing wall azeotropic distillation and extraction of the present invention, wherein the operating conditions of the extraction column are: the temperature at the top of the extraction column is 20-50°C, and the pressure at the top is 0.1-0.3 MPa.

[0026] The method for separating naphthalene aromatic hydrocarbons in a complex system by combining dividing wall azeotropic distillation and extraction of the present invention, wherein the stripping agent has the characteristic of effectively binding the extractant, and at the same time is immiscible with aromatic hydrocarbons, and can separate the extractant and aromatic hydrocarbons. Due to the large boiling point difference between the selected stripping agent and the extractant, the extractant and the stripping agent can be separated by distillation. The stripping agent is selected from at least one of water, C1-C4 alcohols or ketones, preferably at least one of methanol, ethanol, isopropanol and water.

[0027] The method for separating naphthalene aromatic hydrocarbons in a complex system by combining dividing wall azeotropic distillation and extraction of the present invention, wherein the mass ratio of the stripping agent to the feed stream entering the stripping column is (2-4):1.

[0028] The method for separating naphthalene aromatic hydrocarbons in a complex system by combining dividing wall azeotropic distillation and extraction of the present invention, wherein the operating temperature of the stripping column is 20-50°C, and the operating pressure is 0.1-0.3 MPa.

[0029] The method for separating naphthalene aromatic hydrocarbons in a complex system by combining dividing wall azeotropic distillation and extraction of the present invention, wherein the target product includes at least one of methylnaphthalene and dimethylnaphthalene.

[0030] The method for separating naphthalene aromatic hydrocarbons in a complex system by combining dividing wall azeotropic distillation and extraction of the present invention, wherein the intermediate component is the remaining intermediate distillate segment after the extraction of methylnaphthalene and dimethylnaphthalene is completed.

[0031] The method for separating naphthalene aromatic hydrocarbons in a complex system by combining dividing wall azeotropic distillation and extraction of the present invention, wherein the operating conditions of the dividing wall azeotropic distillation column are: the pressure at the top of the column is 0.01-0.05 MPa, and the temperature at the bottom of the column is 180-220°C.

[0032] The method for separating naphthalene aromatic hydrocarbons in a complex system by combining dividing wall azeotropic distillation and extraction of the present invention, wherein the azeotropic agent is a compound composition composed of 1,3-propanediol, ethylene glycol, ethanolamine and water.

[0033] The method for separating naphthalene aromatic hydrocarbons in a complex system by combining dividing wall azeotropic distillation and extraction of the present invention, wherein the mass ratio of the azeotropic agent to the raw material is 0.5-1.2:1.

[0034] The method for separating naphthalene aromatic hydrocarbons in a complex system by combining partition azeotropic distillation and extraction according to the present invention, the operating conditions for phase separation are: temperature 20 - 50°C, pressure 0.1 - 0.3 MPa.

[0035] The present invention also provides a system for separating naphthalene aromatic hydrocarbons in a complex system by combining partition azeotropic distillation and extraction, comprising:

[0036] A partition azeotropic distillation column, with a raw material inlet and an intermediate component outlet provided in the middle, a light component outlet provided on one side of the top, an azeotropic component outlet provided on the other side of the top, and a heavy component outlet provided at the bottom. A partition is provided in the partition azeotropic distillation column, and an azeotropic agent inlet is provided below the partition;

[0037] A phase separator, with one side communicating with the azeotropic component outlet of the partition azeotropic distillation column and the bottom communicating with the azeotropic agent inlet of the partition azeotropic distillation column;

[0038] An extraction column, with the lower part communicating with the top of the phase separator, an extractant inlet provided on one side of the upper part, a paraffin-rich component outlet provided on the other side of the upper part, and an extraction phase outlet provided at the bottom; and

[0039] A solvent recovery column, with an inlet provided in the middle, an outlet provided at the bottom, and a solvent outlet provided at the top. The solvent outlet communicates with the extractant inlet of the extraction column.

[0040] The system for separating naphthalene aromatic hydrocarbons in a complex system by combining partition azeotropic distillation and extraction according to the present invention further includes a back-extraction column. The lower part of the back-extraction column is provided with an extraction phase inlet, and the extraction phase inlet communicates with the extraction phase outlet at the bottom of the extraction column; the upper part of the back-extraction column is provided with a back-extraction agent inlet. At this time, the solvent outlet of the solvent recovery column does not communicate with the extractant inlet of the extraction column, but communicates with the back-extraction agent inlet at the upper part of the back-extraction column; the top of the back-extraction column is provided with a target product outlet, the bottom of the back-extraction column is provided with a back-extraction phase outlet, the back-extraction phase outlet communicates with the inlet in the middle of the solvent recovery column, and the outlet at the bottom of the solvent recovery column communicates with the extractant inlet at the upper part of the extraction column.

[0041] Compared with the prior art, the present invention has at least the following beneficial effects:

[0042] (1) The present invention can be used to process raw materials containing complex components including alkanes, naphthenes, alkylbenzenes, indene, indan, naphthalenes, acenaphthene, and acenaphthylene. Especially for raw materials with a low content of methylnaphthalene + dimethylnaphthalene (<30%), the single extraction method cannot achieve separation. The method of the present invention has good universality.

[0043] (2) For the feed of raw materials with complex components, the separation section of the present invention adopts a dividing wall azeotropic distillation column in the previous stage. By using a single column, the separation of light components, azeotropic components, intermediate components, and heavy components can be achieved, which can save equipment investment and reduce energy consumption.

[0044] (3) The azeotropic agent used in the present invention is a composite formula azeotropic agent, which can form a low-boiling azeotrope with the target products methylnaphthalene and dimethylnaphthalene, so that they can be separated from alkanes and alkylbenzenes with similar boiling points under ordinary distillation conditions, achieving an effect that cannot be achieved under ordinary distillation. At the same time, the azeotropic agent can be naturally phase-separated from the oil phase at room temperature, and has the characteristics of good recovery and recyclability.

[0045] (4) The extractant used in the present invention has excellent aromatic hydrocarbon affinity. Furthermore, a composite extractant formula can be selected, taking into account both selectivity and aromatic hydrocarbon yield, and having a good extraction effect on both methylnaphthalene and dimethylnaphthalene.

[0046] (5) The present invention selects a suitable stripping agent to separate the target product and the extractant through a stripping process, solving the problem that the boiling point difference between the target product and the extractant is small, and it is difficult to achieve separation by distillation with high energy consumption. At the same time, the selected stripping agent is simple and easy to obtain, and the boiling point difference between the stripping agent and the extractant is large, and the stripping agent and the extractant can be recovered and reused through simple distillation. Description of the Drawings

[0047] Figure 1 is a process flow diagram of separating naphthalene-based aromatic hydrocarbons in a complex system by combining dividing wall azeotropic distillation and extraction of the present invention;

[0048] Among them, the description of the reference numerals:

[0049] 1 Dividing wall azeotropic distillation column; 2 Extraction column; 3 Stripping column; 4 Solvent recovery column; 5 Phase separator; 6 Raw material; 7 Azeotropic component; 8 Light component; 9 Oil phase (methylnaphthalene and dimethylnaphthalene enrichment section); 10 Azeotropic agent; 11 Intermediate component; 12 Heavy component; 13 Supplementary fresh extractant; 14 Component rich in alkanes; 15 Extract phase (extractant + target product); 16 Supplementary fresh stripping agent; 17 Target product; 18 Stripping phase; 19 Recovered stripping agent; 20 Recovered extractant.

[0050] Figure 2 is another process flow diagram of separating naphthalene-based aromatic hydrocarbons in a complex system by combining dividing wall azeotropic distillation and extraction of the present invention;

[0051] Among them, the description of the reference numerals:

[0052] 1 Dividing-wall azeotropic distillation column; 2 Extraction column; 4 Solvent recovery column; 5 Phase separator; 6 Feedstock; 7 Azeotropic component; 8 Light component; 9 Oil phase (methylnaphthalene and dimethylnaphthalene enrichment section); 10 Azeotropic agent; 11 Intermediate component; 12 Heavy component; 13 Supplementary fresh extractant; 14 Paraffin-rich component; 15 Extract phase (extractant + target product); 16 Recycled extractant; 17 Target product. Detailed implementation mode

[0053] Figure 1 This is a process flow diagram for separating naphthalene aromatic hydrocarbons in a complex system by combining dividing-wall azeotropic distillation and extraction in the present invention. The system includes a dividing-wall azeotropic distillation column 1, an extraction column 2, a back-extraction column 3, a solvent recovery column 4, and a phase separator 5.

[0054] The middle part of the dividing-wall azeotropic distillation column 1 is provided with a feedstock inlet and an intermediate component outlet. One side of the top is provided with a light component outlet, and the other side of the top is provided with an azeotropic component outlet. The bottom is provided with a heavy component outlet. There is a dividing wall in the dividing-wall azeotropic distillation column 1, and an azeotropic agent inlet is provided below the dividing wall; one side of the phase separator 5 is connected to the azeotropic component outlet of the dividing-wall azeotropic distillation column 1, and the bottom is connected to the azeotropic agent inlet of the dividing-wall azeotropic distillation column 1; the lower part of the extraction column 2 is connected to the top of the phase separator 5, one side of the upper part is provided with an extractant inlet, the other side of the upper part is provided with a paraffin-rich component outlet, and the bottom is provided with an extract phase outlet; the lower part of the back-extraction column 3 is provided with an extract phase inlet, and the extract phase inlet is connected to the extract phase outlet at the bottom of the extraction column 3; the middle part of the solvent recovery column 4 is provided with an inlet, the bottom is provided with an outlet, and the top is provided with a solvent outlet; the upper part of the back-extraction column 3 is provided with a back-extraction agent inlet, and the solvent outlet of the solvent recovery column 4 is connected to the back-extraction agent inlet at the upper part of the back-extraction column 3; the top of the back-extraction column 3 is provided with a target product outlet, the bottom of the back-extraction column 3 is provided with a back-extraction phase outlet, the back-extraction phase outlet is connected to the inlet in the middle part of the solvent recovery column 4, and the outlet at the bottom of the solvent recovery column 4 is connected to the extractant inlet at the upper part of the extraction column 2.

[0055] The method for separating naphthalene aromatic hydrocarbons in a complex system by combining dividing-wall azeotropic distillation and extraction in the present invention includes the following steps:

[0056] Introduce the feedstock containing the target product into the dividing-wall azeotropic distillation column. The feedstock and the azeotropic agent azeotropically distill and separate in the dividing-wall azeotropic distillation column to obtain light components, azeotropic components, intermediate components, and heavy components. The azeotropic agent forms a low-boiling azeotropic component with the target product and is output from the dividing-wall azeotropic distillation column; the azeotropic component is phase-separated by the phase separator to obtain an azeotropic agent phase and an oil phase. The azeotropic agent phase returns to the dividing-wall azeotropic distillation column for recycling, and the oil phase is extracted and separated to obtain the target naphthalene aromatic hydrocarbons.

[0057] The method for separating naphthalene aromatic hydrocarbons in a complex system by combining dividing-wall azeotropic distillation and extraction in the present invention can also be described in detail as follows:

[0058] In this process, the method for separating naphthalene aromatic hydrocarbons in a complex system by combining dividing wall azeotropic distillation and extraction comprises the following steps:

[0059] (1) Feedstock 6 containing the target product is introduced into the middle of dividing wall azeotropic distillation column 1. There is a dividing wall in dividing wall azeotropic distillation column 1, and azeotropic agent 10 is introduced from below the dividing wall. Feedstock 6 and azeotropic agent 10 are azeotropically distilled and separated in dividing wall azeotropic distillation column 1; the separated light components 8 are output from one side of the top of dividing wall azeotropic distillation column 1; azeotropic agent 10 and the target product form a low-boiling azeotropic component 7, and azeotropic component 7 is output from the other side of the top of dividing wall azeotropic distillation column; the separated intermediate components 11 are output from the middle of dividing wall azeotropic distillation column 1; the separated heavy components 12 are output from the bottom of dividing wall azeotropic distillation column 1;

[0060] (2) After passing through phase separator 5, azeotropic component 7 is phase-separated into an azeotropic agent phase and an oil phase 9. The azeotropic agent phase returns to dividing wall azeotropic distillation column 1 for recycling, and the oil phase is input into the lower part of the extraction column;

[0061] (3) Extractant 13 is input from the upper part of extraction column 2. The extractant in the upper part of extraction column 2 and the oil phase 9 input from the lower part of extraction column 2 undergo a multi-stage countercurrent liquid-liquid extraction process to separate the aromatic hydrocarbons and non-aromatics in the oil phase, and a component 14 rich in alkanes is obtained at the top of extraction column 2, and an extraction phase 15 rich in aromatic hydrocarbons and extractant is obtained at the bottom of extraction column 2;

[0062] (4) The extraction phase is input into the lower part of stripping column 3, and the stripping agent is input from the upper part of stripping column 3. Through a multi-stage countercurrent liquid-liquid stripping process, the extractant and aromatic hydrocarbons in extraction phase 15 are separated, and the target product 17, naphthalene aromatic hydrocarbons, is obtained at the top of stripping column 3, and a stripping phase 18 mixed with the extractant is obtained at the bottom of stripping column 3; the stripping phase 18 is input into solvent recovery column 4 for separation, a recovered stripping agent 19 is obtained at the top of solvent recovery column 4, and the recovered stripping agent 19 is input into the upper part of stripping column 3 for recycling, and a recovered extractant 20 is obtained at the bottom of solvent recovery column 4, and the recovered extractant 20 is input into the upper part of extraction column 2 for recycling.

[0063] Preferably, the stripping agent is selected from at least one of water, C1-C4 alcohols or ketones, and more preferably, selected from at least one of methanol, ethanol, isopropanol, and water.

[0064] Preferably, the mass ratio of the stripping agent to the feed stream entering the stripping column is (2-4):1.

[0065] Preferably, the operating temperature of the stripping column is 20-50 °C, and the operating pressure is 0.1-0.3 MPa.

[0066] Figure 2This is the process flow diagram of another azeotropic distillation with partition wall and extraction combined to separate the complex system of naphthalene aromatic hydrocarbons in the present invention. This process is different from Figure 1 that in that an anti-extraction column 3 is not provided. In this process, the selected extractant has a relatively low boiling point and can be directly separated from the target product by distillation. Therefore, after the extraction process is completed, it can enter the solvent recovery column 4 for distillation separation without going through anti-extraction. In this process, the system includes a partition wall azeotropic distillation column 1, an extraction column 2, a solvent recovery column 4 and a phase separator 5.

[0067] In this process, a raw material inlet and an intermediate component outlet are provided in the middle of the partition wall azeotropic distillation column 1. A light component outlet is provided on one side of the top, an azeotropic component outlet is provided on the other side of the top, and a heavy component outlet is provided at the bottom of the column. There is a partition in the partition wall azeotropic distillation column 1, and an azeotropic agent inlet is provided below the partition; one side of the phase separator 5 is communicated with the azeotropic component outlet of the partition wall azeotropic distillation column 1, and the bottom is communicated with the azeotropic agent inlet of the partition wall azeotropic distillation column 1; the lower part of the extraction column 2 is communicated with the top of the phase separator 5, an extractant inlet is provided on one side of the upper part, a paraffin-rich component outlet is provided on the other side of the upper part, and an extraction phase outlet is provided at the bottom; an inlet is provided in the middle of the solvent recovery column 4, an outlet is provided at the bottom, and a solvent outlet is provided at the top. The solvent outlet is communicated with the extractant inlet of the extraction column 2.

[0068] In this process, the method of separating the complex system of naphthalene aromatic hydrocarbons by combining partition wall azeotropic distillation and extraction includes the following steps:

[0069] (1) Introduce the raw material 6 containing the target product into the middle of the partition wall azeotropic distillation column 1. There is a partition in the partition wall azeotropic distillation column 1, and the azeotropic agent 10 is introduced from below the partition. The raw material 6 and the azeotropic agent 10 are azeotropically distilled and separated in the partition wall azeotropic distillation column 1; the separated light component 8 is output from one side of the top of the partition wall azeotropic distillation column 1; the azeotropic agent 10 and the target product form a low-boiling azeotropic component 7, and the azeotropic component 7 is output from the other side of the top of the partition wall azeotropic distillation column 1; the separated intermediate component 11 is output from the middle of the partition wall azeotropic distillation column 1; the separated heavy component 12 is output from the bottom of the partition wall azeotropic distillation column 1;

[0070] (2) After passing through the phase separator 5, the azeotropic component 7 is phase-separated into an azeotropic agent phase and an oil phase 9. The azeotropic agent phase returns to the partition wall azeotropic distillation column 1 for recycling, and the oil phase is input to the lower part of the extraction column;

[0071] (3) The extractant 13 is input from the upper part of the extraction column 2. The extractant in the upper part of the extraction column 2 and the oil phase 9 input from the lower part of the extraction column 2 undergo a multi-stage countercurrent liquid-liquid extraction process to separate the aromatic hydrocarbons and non-aromatics in the oil phase, and a paraffin-rich component 14 is obtained at the top of the extraction column 2, and an extraction phase 15 rich in aromatic hydrocarbons and extractant is obtained at the bottom of the extraction column 2;

[0072] (4) Feed the extraction phase 15 into the solvent recovery column 4 for separation. The recycled extractant 16 is obtained at the top of the solvent recovery column 4, and the recycled extractant 16 is fed into the upper part of the extraction column 2 for recycling. The target product 17, naphthalene-based aromatic hydrocarbons, is obtained at the bottom of the solvent recovery column 4.

[0073] Preferably, the target product includes at least one of methylnaphthalene and dimethylnaphthalene.

[0074] Preferably, in step (1), the operating conditions of the dividing-wall azeotropic distillation column are as follows: the top pressure is 0.01 - 0.05 MPa, and the bottom temperature is 180 - 220 °C.

[0075] Preferably, the azeotropic agent is a compound composition composed of 1,3 - propanediol, ethylene glycol, ethanolamine, and water.

[0076] Preferably, the mass ratio of the azeotropic agent to the raw material is 0.8:1.

[0077] Preferably, in step (2), the operating conditions for phase separation are: 20 - 50 °C, and the pressure is 0.1 - 0.3 MPa.

[0078] Preferably, the extractant is selected from at least one of furfural, sulfolane, dimethyl sulfoxide (DMSO), and N,N - dimethylformamide (DMF).

[0079] Preferably, the mass ratio of the extractant to the feed material of the extraction column is 2 - 4:1.

[0080] Preferably, in step (3), the operating conditions of the extraction column are: the top temperature of the extraction column is 20 - 50 °C, and the top pressure is 0.1 - 0.3 MPa.

[0081] The present invention will be further described in detail below with specific embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0082] Example 1

[0083] The feed composition of this example is shown in Table 1.

[0084] This example adopts the process flow chart as shown in Figure 1 . The number of theoretical plates of the dividing-wall azeotropic distillation column of the present invention is 60, and the designed structure is the structure with the dividing wall located at the top of the column. The position of the raw material feed plate is the 30th plate, and the position of the azeotropic agent feed plate is the 40 - 50th plates. The operating conditions in the dividing-wall azeotropic distillation column are: the top pressure is 0.01 MPa, and the bottom temperature is 206 °C.

[0085] The azeotropic agent used in this example is a composite formula azeotropic agent, with the composition of 50 wt% of 1,3 - propanediol + 40 wt% of ethylene glycol + 5 wt% of ethanolamine + 5 wt% of water. The mass ratio of the azeotropic agent to the raw material is 0.8:1.

[0086] In this embodiment, the operating conditions of the phase separator are a temperature of 40 °C and a pressure of 0.1 MPa.

[0087] The extractant used in this embodiment is a mixed extractant of 75 wt% sulfolane + 25 wt% DMF. The number of theoretical plates in the extraction column is 40 plates. The mass ratio of the extractant to the feed stream entering the extraction column is 3:1. The temperature at the top of the extraction column is 45 °C, and the pressure at the top of the extraction column is 0.12 MPa. The number of theoretical plates in the stripping column is 40 plates. The mass ratio of the stripping column to the feed stream entering the stripping column is 2.5:1. The temperature at the top of the stripping column is 45 °C, and the top pressure is 0.12 MPa. The number of theoretical plates in the solvent recovery column is 20 plates, and the power of the reboiler in the solvent recovery column is 285 KW.

[0088] The raw materials are first separated by a dividing-wall azeotropic distillation column to remove light components, intermediate components, and heavy components. The target product is enriched in the azeotropic components. After passing through the dividing-wall azeotropic distillation column, the content of methylnaphthalene + dimethylnaphthalene increases from 20.16 wt% in the raw materials to 74.5 wt%. The raw material composition and the composition after passing through the dividing-wall azeotropic distillation column are shown in Table 1.

[0089] After being cut by the dividing-wall column, the intermediate components pass through the solvent extraction column. The extractant extracts the aromatic hydrocarbons and then introduces them into the stripping column. In the stripping column, the stripping agent combines with the extractant, thereby separating the extractant from the mixed aromatic hydrocarbons. The target product is obtained at the top of the stripping column, where the content of the mixed aromatic hydrocarbons is 99.8 wt%, the content of methylnaphthalene + dimethylnaphthalene is 96.31 wt%, and the recovery rate of the mixed aromatic hydrocarbons is 92.3%. The stripping agent and the extractant are distilled in the solvent recovery column and separated according to the difference in boiling points. 97.86 wt% of the recovered stripping agent can be obtained at the top of the solvent recovery column and returned to the stripping column for recycling. The recovery rate of the stripping agent is 99.9%. 97.1 wt% of the recovered extractant can be obtained at the bottom of the solvent recovery column and returned to the extraction column for recycling. The recovery rate of the extractant is 98.9%. The composition of the target product, the purity and recovery rate of the recovered extractant / stripping agent, and the design parameters of each column in Example 1 are shown in Table 2. The ranking of the aromatic selectivity, recovery rate, stripping difficulty, and solvent recovery difficulty of the four examples is shown in Table 3.

[0090] Example 2

[0091] The feed composition of this embodiment is shown in Table 1.

[0092] This embodiment uses a Figure 1 process flow chart as shown. The number of theoretical plates in the dividing-wall column of the present invention can be 60 plates, and the design structure is a design structure with the dividing wall located in the tower. The feed plate position can be the 30th plate. The operating conditions in the dividing-wall azeotropic distillation column are: the top pressure is 0.01 MPa, and the bottom temperature is 206 °C.

[0093] In this embodiment, the operating conditions of the phase separator are a temperature of 40 °C and a pressure of 0.1 MPa.

[0094] The azeotropic agent used in this embodiment is a composite formula azeotropic agent, with a composition of 40 wt% 1,3-propanediol + 20 wt% ethylene glycol + 30 wt% ethanolamine + 10 wt% water. The mass ratio of the azeotropic agent to the raw material is 0.9:1.

[0095] The extractant used in this embodiment is a mixed extractant of 75 wt% DMF + 25 wt% DMSO. The number of theoretical plates in the extraction column is 40 plates. The mass ratio of the extractant to the feed stream entering the extraction column is 2:1. The top temperature of the extraction column is 45 °C, and the top pressure of the extraction column is 0.12 MPa. The number of theoretical plates in the stripping column is 50 plates. The mass ratio of the stripping column to the feed stream entering the stripping column is 4:1. The top temperature of the stripping column is 45 °C, and the top pressure is 0.12 MPa. The number of theoretical plates in the solvent recovery column is 20 plates, and the reboiler power of the solvent recovery column is 359.1 KW.

[0096] The raw material is first separated in a dividing wall azeotropic distillation column to remove light components, intermediate components, and heavy components. The target product is enriched in the azeotropic components. After passing through the dividing wall azeotropic distillation column, the content of methylnaphthalene + dimethylnaphthalene increases from 20.16 wt% in the raw material to 74.5%. The raw material composition and the composition after passing through the dividing wall azeotropic distillation column are shown in Table 1.

[0097] After being cut by the dividing wall column, the intermediate components pass through a solvent extraction column. The extractant extracts the aromatics and introduces them into the stripping column. In the stripping column, the stripping agent combines with the extractant to separate the extractant and the mixed aromatics. The target product is obtained at the top of the stripping column, where the content of the mixed aromatics is 96.3 wt%, the content of methylnaphthalene + dimethylnaphthalene is 91.0 wt%, and the recovery rate of the mixed aromatics is 95.4%. The stripping agent and the extractant are distilled in the solvent recovery column and separated according to the difference in boiling points. 95.7 wt% of the recovered stripping agent can be obtained at the top of the solvent recovery column and returned to the stripping column for recycling. The recovery rate of the stripping agent is 99%. 97.1 wt% of the recovered extractant can be obtained at the bottom of the solvent recovery column and returned to the extraction column for recycling. The recovery rate of the extractant is 98.9%. The composition of the target product, the purity and recovery rate of the recovered extractant / stripping agent, and the design parameters of each column in Example 2 are shown in Table 2. The ranking of the aromatic selectivity, recovery rate, stripping difficulty, and solvent recovery difficulty of the four examples is shown in Table 3.

[0098] Example 3

[0099] The feed composition of this embodiment is shown in Table 1.

[0100] This embodiment uses as Figure 2For the process flow diagram shown, the number of theoretical plates of the dividing wall column in the present invention can be 60, and the design structure is that the dividing wall is located in the middle of the column. The feed plate position can be the 30th plate. The operating conditions in the dividing wall azeotropic distillation column are as follows: the top pressure of the column is 0.01 MPa, and the bottom temperature of the column is 206 °C.

[0101] In this embodiment, the operating conditions of the phase separator are a temperature of 40 °C and a pressure of 0.1 MPa.

[0102] The azeotropic agent used in this embodiment is 80 wt% 1,3 - propanediol + 10 wt% ethylene glycol + 5 wt% ethanolamine + 5 wt% water, and the mass ratio of the azeotropic agent to the raw material is 1.2:1.

[0103] The extractant used in this embodiment is a single extractant of 100 wt% furfural. The number of theoretical plates in the extraction column is 40 plates. The mass ratio of the extractant to the feed stream of the extraction column is 4:1. The top temperature of the extraction column is 45 °C, and the top pressure of the extraction column is 0.12 MPa. The boiling point of the extractant selected in this embodiment is relatively low and can be directly separated from the target product by distillation. Therefore, after the extraction process is completed, it can enter the solvent recovery column for distillation separation without passing through back - extraction.

[0104] The number of theoretical plates of the solvent recovery column selected in this embodiment is 20 plates, and the power of the reboiler of the solvent recovery column is 222 KW.

[0105] The raw material is first separated in the dividing wall azeotropic distillation column to remove light components, intermediate components, and heavy components. The target product is enriched in the azeotropic components. After passing through the dividing wall azeotropic distillation column, the content of methylnaphthalene + dimethylnaphthalene increases from 20.16 wt% in the raw material to 74.5 wt%. The raw material composition and the composition after passing through the dividing wall azeotropic distillation column are shown in Table 1.

[0106] After being cut by the dividing wall column, the intermediate components pass through the solvent extraction column. The extractant extracts the aromatic hydrocarbons and then introduces them into the solvent recovery column. After distillation in the solvent recovery column, the target product and the extractant are separated according to the boiling point difference. The target product is obtained at the bottom of the solvent recovery column, where the content of mixed aromatic hydrocarbons is 94.2 wt%, the content of methylnaphthalene + dimethylnaphthalene is 88.55 wt%, and the recovery rate of mixed aromatic hydrocarbons is 89.6%. 99.2 wt% of the recovered extractant can be obtained at the top of the solvent recovery column and returned to the extraction column for recycling use, and the recovery rate of the extractant is 99.1%. The composition of the target product, the purity and recovery rate of the recovered extractant / back - extraction agent, and the design parameters of each column in Example 3 are shown in Table 2. The ranking of the aromatic hydrocarbon selectivity, recovery rate, ease of back - extraction, and ease of solvent recovery for the four examples is shown in Table 3.

[0107] Example 4

[0108] The feed composition of this embodiment is shown in Table 1.

[0109] This embodiment adopts the process flow chart as shown in Figure 1 The theoretical number of plates of the dividing wall column described in the present invention can be 60, and the designed structure is that the dividing wall is located in the middle of the column. The feed plate position can be the 30th plate. The operating conditions in the dividing wall azeotropic distillation column are as follows: the top pressure of the column is 0.01 MPa, and the bottom temperature of the column is 206 °C.

[0110] The operating conditions of the phase separator in this embodiment are a temperature of 40 °C and a pressure of 0.1 MPa.

[0111] The azeotropic agent adopted in this embodiment is 50 wt% of 1,3 - propanediol + 25 wt% of ethylene glycol + 20 wt% of ethanolamine + 5 wt% of water, and the mass ratio of the azeotropic agent to the raw material is 0.5:1.

[0112] The extractant adopted in this embodiment is a mixed extractant of 65 wt% of sulfolane + 35 wt% of furfural. The theoretical number of plates of the extraction column is 40 plates. The mass ratio of the extractant to the feed stream of the extraction column is 3:1. The top temperature of the extraction column is 45 °C, and the top pressure of the extraction column is 0.12 MPa. The theoretical number of plates of the stripping column is 35 plates. The mass ratio of the stripping column to the feed stream entering the stripping column is 3:1. The top temperature of the stripping column is 45 °C, and the top pressure is 0.12 MPa. The theoretical number of plates of the solvent recovery column is 20 plates, and the power of the reboiler of the solvent recovery column is 213.75 KW.

[0113] The raw material first undergoes separation in the dividing wall azeotropic distillation column to remove light components, intermediate components, and heavy components. The target product is enriched in the azeotropic components. After passing through the dividing wall azeotropic distillation column, the content of methylnaphthalene + dimethylnaphthalene increases from 20.16 wt% in the raw material to 74.5 wt%. The raw material composition and the composition after passing through the dividing wall azeotropic distillation column are shown in Table 1.

[0114] After being cut by the dividing wall column, the intermediate components pass through the solvent extraction column. The extractant extracts the aromatic hydrocarbons and then introduces them into the stripping column. In the stripping column, the stripping agent combines with the extractant, thereby separating the extractant from the mixed aromatic hydrocarbons. The target product is obtained at the top of the stripping column, where the content of the mixed aromatic hydrocarbons is 98.7 wt%, the content of methylnaphthalene + dimethylnaphthalene is 93.77 wt%, and the recovery rate of the mixed aromatic hydrocarbons is 85%. The stripping agent and the extractant are distilled in the solvent recovery column and separated according to the difference in boiling points. 99.1 wt% of the recovered stripping agent can be obtained at the top of the solvent recovery column and returned to the stripping column for recycling. The recovery rate of the stripping agent is 99.9%. 98.4 wt% of the recovered extractant can be obtained at the bottom of the solvent recovery column and returned to the extraction column for recycling. The recovery rate of the extractant is 99.1%. The composition of the target product, the purity and recovery rate of the recovered extractant / stripping agent, and the design parameters of each column in Example 4 are shown in Table 2. The ranking of the aromatic selectivity, aromatic recovery rate, stripping difficulty, and solvent recovery difficulty of the four examples is shown in Table 3.

[0115] Comparative Example 1

[0116] It is different from Example 1 in that no azeotropic agent is added. Others are the same as Example 1.

[0117] Table 1. Feed composition of raw materials and composition of intermediate components after separation by dividing wall column

[0118]

[0119]

[0120] Table 2. Product composition of each example, purity and recovery rate of recycled extractant / stripping agent, and design parameters of each column

[0121]

[0122]

[0123]

[0124] Table 3. Ranking of aromatic selectivity, aromatic yield, ease of stripping, and ease of solvent recovery of each example

[0125]

[0126] Of course, the present invention may also have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding changes and deformations should all fall within the protection scope of the present invention.

Claims

1. A method for separating complex system naphthalene aromatics by combining baffle azeotropic distillation and extraction, comprising the following steps: The raw materials including the target product are introduced into a baffle azeotropic distillation tower, the raw materials and the entrainer are azeotropically separated in the baffle azeotropic distillation tower to obtain a light component, an azeotropic component, an intermediate component, and a heavy component, and the entrainer and the target product form a low-boiling azeotrope component and output the baffle azeotropic distillation tower; The azeotropic components are separated into an entrainer phase and an oil phase after passing through a phase separator, the entrainer phase is returned to the baffle azeotropic distillation tower for recycling, and the oil phase is extracted and separated to obtain the target product, naphthalene aromatics; The azeotropic agent is a composite composition consisting of 1,3-propylene glycol, ethylene glycol, ethanolamine and water.

2. The method according to claim 1, characterized in that The mass proportions of 1,3-propylene glycol, ethylene glycol, ethanolamine and water in the azeotropic agent are: 40-80% of 1,3-propylene glycol, 10-40% of ethylene glycol, 5-30% of ethanolamine and 5-10% of water.

3. The method according to claim 1, characterized in that The raw materials including the target product are introduced into the middle part of the baffle azeotropic distillation tower, the baffle azeotropic distillation tower is provided with a baffle, and the azeotropic agent is introduced from below the baffle; The separated light component is output from one side of the top of the baffle azeotropic distillation tower; the azeotropic component is output from the other side of the top of the baffle azeotropic distillation tower; the separated intermediate component is output from the middle of the baffle azeotropic distillation tower; and the separated heavy component is output from the bottom of the baffle azeotropic distillation tower.

4. The method according to claim 1, characterized in that The extraction comprises the following steps: The oil phase is input into the lower part of the extraction tower, and the extractant is input from the upper part of the extraction tower. The extractant in the upper part of the extraction tower and the oil phase input from the lower part of the extraction tower are subjected to a multi-stage countercurrent liquid-liquid extraction process to separate aromatic hydrocarbons from non-aromatic hydrocarbons in the oil phase, and a component rich in alkanes is obtained at the top of the extraction tower, and an extract phase rich in aromatic hydrocarbons and the extractant is obtained at the bottom of the extraction tower; The separation comprises the following steps: The extraction phase is input into a solvent recovery tower for separation, and a recovered extractant is obtained at the top of the solvent recovery tower. The recovered extractant is input into the upper part of the extraction tower for recycling, and the target product, naphthalene aromatics, is obtained at the bottom of the solvent recovery tower.

5. The method according to claim 4, characterized in that The separation also includes a stripping process, which specifically includes the following steps: The extract phase is input into the lower part of the stripping tower, and the stripping agent is input from the upper part of the stripping tower. After a multi-stage countercurrent liquid-liquid stripping process, the extractant and aromatic hydrocarbons in the extract phase are separated, and the target product naphthalene aromatic hydrocarbons are obtained at the top of the stripping tower, and the stripping phase mixed with the extractant is obtained at the bottom of the stripping tower; The stripping phase is input into a solvent recovery tower for separation, a recovered stripping agent is obtained at the top of the solvent recovery tower, the recovered stripping agent is input into the upper part of the stripping tower for recycling, and a recovered extracting agent is obtained at the bottom of the solvent recovery tower, the recovered extracting agent is input into the upper part of the extraction tower for recycling.

6. The method according to claim 4 or 5, characterized in that: The extractant is selected from at least one of furfural, sulfolane, dimethyl sulfoxide (DMSO), and N,N-dimethylformamide (DMF).

7. The method according to claim 4 or 5, characterized in that: The mass ratio of the extractant to the extraction tower feed stream is 2 to 4:

1.

8. The method according to claim 4 or 5, characterized in that: The operating conditions of the extraction tower are: the top temperature of the extraction tower is 20-50° C., and the top pressure is 0.1-0.3 MPa.

9. The method according to claim 5, characterized in that The stripping agent is selected from at least one of water, C1-C4 alcohols or ketones.

10. The method according to claim 9, characterized in that The stripping agent is selected from at least one of methanol, ethanol, isopropanol and water.

11. The method according to claim 5, characterized in that The mass ratio of the stripping agent to the feed stream entering the stripping tower is (2-4):

1.

12. The method according to claim 5, characterized in that The operating temperature of the stripping tower is 20-50° C., and the operating pressure is 0.1-0.3 MPa.

13. The method according to claim 1, characterized in that The target product includes at least one of methylnaphthalene and dimethylnaphthalene.

14. The method according to claim 1, characterized in that The operating conditions of the baffle azeotropic distillation tower are: the tower top pressure is 0.01-0.05 MPa, and the tower bottom temperature is 180-220°C.

15. The method according to claim 1, characterized in that The mass ratio of the entrainer to the raw material is 0.5-1.2:

1.

16. The method according to claim 1, characterized in that The operating conditions of the phase separation are: temperature 20-50° C., pressure 0.1-0.3 MPa.

17. A system for separating complex system naphthalene aromatics by combining baffle azeotropic distillation and extraction, characterized in that: include: A partition azeotropic distillation tower is provided with a raw material inlet and an intermediate component outlet in the middle, a light component outlet is provided on one side of the top, an azeotropic component outlet is provided on the other side of the top, and a heavy component outlet is provided at the bottom of the tower. A partition is provided in the partition azeotropic distillation tower, and an azeotropic agent inlet is provided below the partition; A phase separator, one side of which is connected to the azeotropic component outlet of the baffle azeotropic distillation tower, and the bottom of which is connected to the azeotropic agent inlet of the baffle azeotropic distillation tower; An extraction tower, the lower part of which is connected to the top of the phase separator, one side of the upper part is provided with an extractant inlet, the other side of the upper part is provided with an alkane-rich component outlet, and the bottom is provided with an extraction phase outlet; and The solvent recovery tower has an inlet in the middle, an outlet at the bottom and a solvent outlet at the top, and the solvent outlet is connected to the extractant inlet of the extraction tower.

18. The system according to claim 17, characterized in that It also includes a stripping tower, wherein the lower portion of the stripping tower is provided with an extraction phase inlet, and the extraction phase inlet is connected to the extraction phase outlet at the bottom of the extraction tower; the upper portion of the stripping tower is provided with a stripping agent inlet, and at this time, the solvent outlet of the solvent recovery tower is not connected to the extractant inlet of the extraction tower, but is connected to the stripping agent inlet at the upper portion of the stripping tower; the top of the stripping tower is provided with a target product outlet, the bottom of the stripping tower is provided with a stripping phase outlet, the stripping phase outlet is connected to the inlet in the middle portion of the solvent recovery tower, and the outlet at the bottom of the solvent recovery tower is connected to the extractant inlet at the upper portion of the extraction tower.

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