Apparatus and method for separating and purifying styrene from crude mixture comprising styrene

Abstract

An apparatus, in particular for separating and purifying styrene from a crude mixture comprising styrene, comprises a steam generating unit and a divided wall distillation column wherein the divided wall distillation column comprises a divided wall comprising a first portion, the first portion extends at least substantially vertically downward from a point located below the top of the distillation column to a point located above the bottom of the divided wall distillation column so as to subdivide the divided wall distillation column into: a top section located above the dividing wall; a bottom section below the partition wall; and a middle section comprising a first middle sub-section on one side of the first portion of the partition wall and a second middle sub-section on an opposite side of the first portion of the partition wall, where the partition wall further comprises a second portion connected to an upper portion of the first portion of the partition wall, at least one part of the bottom section, which extends at least over 10% of the height of the divided wall distillation column, has a smaller cross-sectional area than the middle section of the divided wall distillation column, and wherein at least one part of the bottom section, which extends at least over 10% of the height of the divided wall distillation column, has a smaller cross-sectional area than the middle section of the divided wall distillation column, the dividing wall type distillation column further comprises a feed inlet pipeline, an extraction solvent inlet pipeline, a steam inlet pipeline connected with the steam generating unit, an overhead outlet pipeline, a bottom outlet pipeline and a side outlet pipeline connected with the second middle sub-section of the dividing wall type distillation column, the plant further comprises a side condenser and a liquid-liquid separator, where the side outlet line is connected to the side condenser and downstream thereof to the liquid-liquid separator, where the liquid-liquid separator is connected to the water line leading into the steam generating unit.

Description

Technical Field

[0001] The present invention relates to an apparatus and a method for separating and purifying styrene from a crude mixture comprising styrene. Background Art

[0002] Styrene is an important building block in polymers such as polystyrene, acrylonitrile-butadiene-styrene / styrene-acrylonitrile resins, styrene-butadiene copolymer latex, unsaturated polyester resins, styrene-butadiene rubber elastomers, and latex. It is one of the most highly traded commodity chemicals; over 30% of annual styrene production is traded internationally. Styrene is primarily produced using benzene and ethylene as feedstocks, where benzene is alkylated with ethylene to form ethylbenzene, and ethylbenzene is converted to styrene via a dehydrogenation process or an ethylbenzene / styrene monomer process or a propylene oxide / styrene monomer process, respectively. Typically, styrene plants are located near ethylene crackers due to ethylene's gaseous nature, which makes it relatively difficult to transport compared to benzene.

[0003] In addition to dedicated production routes via the ethylbenzene / styrene monomer process or the propylene oxide / styrene monomer process, styrene is also present in hydrocarbon streams such as pyrolysis gasoline obtained from the steam cracking of naphtha, hydrocarbon fractions obtained from the thermal or catalytic pyrolysis of waste polystyrene, and unsaturated gasoline obtained from the thermal or catalytic pyrolysis of various waste plastics. Styrene extraction from these hydrocarbon streams presents an economically attractive opportunity for operators due to the low cost of the raw materials. The field of styrene production from waste polystyrene has garnered particular attention due to the current global challenge of plastics recycling. Waste plastics pose a significant environmental threat. However, such separation is technically difficult due to the presence of molecules with similar boiling points and impurities from the starting materials. For example, during polystyrene recycling, different types of waste polystyrene are fed into catalytic or pyrolysis reactors. Due to the contamination of waste plastics coupled with the production of other close boiling point compounds (e.g., benzene, toluene, ethylbenzene, α-methylstyrene, isopropylbenzene, n-propylbenzene, etc.) produced during the pyrolysis or catalytic steps, a reliable method is needed to purify this styrene oil to the final ASTM grade styrene specifications.

[0004] Separating and purifying styrene from a crude mixture containing styrene (such as that produced using any of the aforementioned processes) is typically performed using one or more distillation steps, optionally in conjunction with a liquid / liquid extraction step. In some of these methods, extractive distillation is used, in which the crude mixture is distilled in the presence of an extractant, typically a miscible, relatively non-volatile component with a relatively high boiling point. The extractant changes the fugacity of appropriate components in the crude mixture, where fugacity is the corrected partial vapor pressure of the mixture. This facilitates the separation of substances that would be extremely difficult to separate using conventional distillation due to their similar boiling points. These extractive distillation-based purification processes typically utilize two or three columns and are energy-intensive, requiring high capital expenditures (CAPEX). To reduce the temperature required for extractive distillation, steam is often added to the distillation column as a desorbent, in addition to the crude mixture containing styrene and the extractant. Naturally, steam generation is an energy-intensive process.

[0005] In view of the above, an object underlying the present invention is to provide a plant for separating and purifying styrene from a crude mixture comprising styrene, which plant has only low energy requirements during its operation, requires low CAPEX and allows the production of very pure styrene compositions. Summary of the Invention

[0006] According to the present invention, this object is met by providing an apparatus for separating and purifying styrene from a crude mixture comprising styrene, wherein the apparatus comprises a steam generating unit and a dividing wall distillation column, wherein the dividing wall distillation column comprises a dividing wall, the dividing wall comprising a first portion extending at least substantially vertically downwards from a point below the top of the distillation column to a point above the bottom of the dividing wall distillation column so as to subdivide the dividing wall distillation column into: a top section above the dividing wall; a bottom section below the dividing wall; and a middle section comprising a first middle subsection on one side of the first portion of the dividing wall and a second middle subsection on the opposite side of the first portion of the dividing wall, wherein the dividing wall further comprises a second portion which extends at least substantially vertically downwards from a point below the top of the distillation column to a point above the bottom of the dividing wall distillation column The dividing wall column is connected to an upper part of the first part of the dividing wall column and extends into the second middle subsection as far as the inner wall of the dividing wall column, wherein at least a part of the bottom section, preferably extending over at least 10% of the height of the dividing wall column, has a smaller cross-sectional area than the middle section of the dividing wall column, wherein the dividing wall column further comprises an inlet line for feed, an inlet line for extractive solvent, an inlet line for steam connected to a steam generation unit, a top outlet line, a bottom outlet line, and a side outlet line connected to the second middle subsection of the dividing wall column, wherein the apparatus further comprises a side condenser and a liquid-liquid separator, wherein the side outlet line is connected to the side condenser and connected downstream thereof to the liquid-liquid separator, wherein the liquid-liquid separator is connected to a water line leading to the steam generation unit.

[0007] This solution is based on the surprising discovery that styrene is separated and purified from a crude mixture comprising styrene in an apparatus described above. Specifically, the apparatus is characterized by using a central dividing wall column, wherein the dividing wall has a portion extending toward the inner wall into the central subsection, thereby at least partially enclosing this subsection in an upward direction; and the dividing wall column has a bottom section, at least a portion of which has a smaller cross-sectional area than the central section of the dividing wall column, resulting in particularly low energy requirements and a particularly low capital expenditure (CAPEX). While the particularly low energy requirements are particularly due to the relatively low steam consumption of the apparatus during operation, the particularly low CAPEX is due to the fact that the apparatus requires only one distillation column, namely the dividing wall column. Furthermore, the apparatus according to the present invention requires minimal floor space, particularly because, in addition to the dividing wall column, a further distillation column for recovering the extractant from the mixture of extractant and styrene is unnecessary. This reduces the overall distillation column height, i.e., the sum of the heights of all distillation columns in the apparatus. Furthermore, the apparatus according to the invention surprisingly allows the production of very pure styrene compositions, ie compositions having a styrene content of 95 to 99% by weight, such as up to at least 96.3% by weight.

[0008] According to the present invention, the dividing wall of a dividing wall distillation column includes a first portion that extends at least substantially vertically downward from a point below the top of the distillation column to a point above the bottom of the dividing wall distillation column, thereby subdividing the dividing wall distillation column into: a top section located above the dividing wall; a bottom section located below the dividing wall; and a middle section comprising a first middle sub-section located on one side of the first section of the dividing wall and a second middle sub-section located on the opposite side of the first section of the dividing wall. This means that the top section is the section located above the uppermost point of the dividing wall, as viewed along the length of the dividing wall distillation column (which is the vertical direction), the bottom section is the section located below the lowermost point of the dividing wall, and the middle section is the section located between the top and bottom sections. Thus, the dividing wall distillation column, as viewed from its top to its bottom, consists of a top section, a middle section, and a bottom section.

[0009] At least a portion of the bottom section has a smaller cross-sectional area than the middle section of the dividing wall column. This means that if the middle section has the same (i.e., constant) cross-sectional area throughout its entire height, at least one subsection of the bottom section has a smaller cross-sectional area than the middle section of the dividing wall column. If the middle section does not have a constant, but rather a varying, cross-sectional area throughout its height, at least one subsection of the bottom section has a smaller cross-sectional area than the average cross-sectional area of ​​the middle section of the dividing wall column. The average cross-sectional area of ​​the middle section of the dividing wall column can be calculated by dividing the middle section along its longitudinal direction into subsections, for example, each having a length of 1 cm, measuring the cross-sectional area of ​​each subsection, summing the cross-sectional areas of all subsections, and dividing the resulting sum by the number of subsections. If both the middle section and the bottom section do not have a constant but rather a varying cross-sectional area over their entire height, at least one subsection of the bottom section has an average cross-sectional area that is smaller than the average cross-sectional area of ​​the middle section of the dividing wall column.

[0010] According to the present invention, preferably, at least a portion of the bottom section extending over at least 10% of the height of the dividing wall column has a smaller cross-sectional area than the middle section of the dividing wall column. This means that: if the entire bottom section has a smaller cross-sectional area, the bottom section of the dividing wall column extends over at least 10% of the height of the dividing wall column; if a portion of the bottom section has a smaller cross-sectional area, the portion of the bottom section of the dividing wall column extends over at least 10% of the height of the dividing wall column; and if two or more portions of the bottom section have smaller cross-sectional areas, the sum of the two or more portions extends over at least 10% of the height of the dividing wall column. Preferably, the at least one portion of the bottom section having a smaller cross-sectional area than the middle section of the dividing wall column extends over at least 10% to 50%, and preferably 10% to 25%, of the height of the dividing wall column.

[0011] Preferably, the lowermost subsection of the bottom section is dome-shaped, wherein, seen in the longitudinal direction of the dividing wall distillation column, the lowermost dome-shaped subsection of the bottom section extends over less than 50%, more preferably less than 30%, still more preferably less than 20% and most preferably less than 10% of the section(s) of the bottom section having a smaller cross-sectional area than the middle section of the dividing wall distillation column.

[0012] According to the present invention, the first portion of the dividing wall of the dividing wall column extends at least substantially vertically downward. Preferably, the angle between the first portion of the dividing wall and the longitudinal axis of the top dividing wall column is at most 20°, more preferably at most 10°, even more preferably at most 5°, and most preferably 0°. The longitudinal axis of the dividing wall column is a vertical axis. Furthermore, it is preferred that the first portion of the dividing wall is a plate.

[0013] In a further development of the concept of the invention, it is proposed that the first portion of the dividing wall, seen from the bottom to the top of the dividing wall column, extends from a point located at 10% to 45% of the distance from the bottom to the top of the dividing wall column to a point located at 50% to 90% of the distance from the bottom to the top of the dividing wall column. Even more preferably, the first portion of the dividing wall, seen from the bottom to the top of the dividing wall column, extends from a point located at 25% to 40% of the distance from the bottom to the top of the dividing wall column to a point located at 50% to 75% of the distance from the bottom to the top of the dividing wall column.

[0014] The first portion of the dividing wall subdivides the middle section of the dividing wall column, preferably subdividing the middle section of the dividing wall column in a fluid-tight manner into a first middle subsection and a second middle subsection. This means that the first portion of the dividing wall (preferably a plate) extends over a length section of the dividing wall column, i.e., from a point on the inner wall of the dividing wall column to the opposite inner wall. Good results are particularly achieved when the first portion of the dividing wall, as seen from the bottom to the top of the dividing wall column, extends over 5% to 50% of the distance from the bottom to the top of the dividing wall column (i.e., the length of the dividing wall column), more preferably over 10% to 40%, and even more preferably over 15% to 30%.

[0015] According to a further preferred embodiment of the present invention, the first portion of the dividing wall subdivides the middle section of the dividing wall column into approximately two equally sized subsections or halves, as viewed in cross-section of the dividing wall column. Thus, preferably, one of the first and second middle subsections covers at least 30%, more preferably at least 40%, even more preferably at least 45%, and most preferably 50% of the total cross-sectional area of ​​the middle section of the dividing wall column, while the other of the first and second middle subsections covers the remaining 100% of the total cross-sectional area of ​​the middle section of the dividing wall column. For example, one subsection covers 43% of the total cross-sectional area and the other subsection covers 57% of the total cross-sectional area, or both subsections each cover exactly 50% of the total cross-sectional area. If the total cross-sectional area of ​​the middle section varies over the axial length of the middle section, the above values ​​relate to the average total cross-sectional area of ​​the middle section.

[0016] According to the present invention, the second portion of the dividing wall extends into the second middle subsection as far as the inner wall of the dividing wall column. Preferably, the second portion of the dividing wall is connected to the upper portion of the first portion of the dividing wall and extends into the second middle subsection as far as the inner wall of the dividing wall column, thereby at least partially closing the top of the second middle subsection of the dividing wall column. As a result, the top of the second middle subsection of the dividing wall column is at least partially closed, while the top of the first middle subsection is open. Preferably, the second portion of the dividing wall is connected at one of its ends to the uppermost portion of the first portion of the dividing wall and at the opposite end to the inner wall.

[0017] Even more preferably, the second portion of the dividing wall is connected to the upper portion (most preferably the uppermost portion) of the first portion of the dividing wall, extends into the second middle subsection up to the inner wall of the dividing wall column, and is connected to the inner wall of the dividing wall column so as to fluid-tightly seal the entire top portion of the second middle subsection of the dividing wall column. That is, the second portion covers the entire top portion of the second middle subsection of the dividing wall column. In contrast, the top portion of the first middle subsection of the dividing wall column is open because it is not covered at all by elements such as the second portion of the dividing wall. The fluid-tight sealing of the entire top portion of the second middle subsection of the dividing wall column means that during operation of the dividing wall column, no ascending fluid (gas and / or liquid) can exit the second middle subsection upward, and no descending fluid (gas and / or liquid) can enter the second middle subsection from above.

[0018] Preferably, both parts of the dividing wall are plates. Furthermore, preferably, the first part of the dividing wall comprises an upper edge and a lower edge, and the second part of the dividing wall comprises a first edge and a second edge, wherein the upper edge of the first part of the dividing wall and the first edge of the second part of the dividing wall are connected to each other over the entire length of the two edges, and wherein the second edge of the second part of the dividing wall is connected to the inner wall of the dividing wall column in a fluid-tight manner.

[0019] In a further development of the concept of the present patent application, it is proposed that the second section of the dividing wall extends at least essentially horizontally to the inner wall of the dividing wall column, wherein the angle between the second section of the dividing wall and the cross-sectional plane of the top dividing wall column is preferably at most 20°, more preferably at most 10°, still more preferably at most 5° and most preferably 0°.

[0020] According to the present invention, at least a portion of the bottom section of the dividing wall column has a smaller cross-sectional area than the middle section of the dividing wall column. Preferably, the cross-sectional area of ​​the at least a portion of the bottom section of the dividing wall column is 10% to 99%, more preferably 20% to 95%, even more preferably 30% to 90%, and most preferably 40% to 60% of the cross-sectional area of ​​the middle section. Furthermore, it is preferred that the middle section has at least a substantially constant cross-sectional area along its length (i.e., along the vertical axis or the longitudinal axis, respectively, of the dividing wall column). In this context, a substantially constant cross-sectional area means that the difference between the maximum and minimum cross-sectional areas along the vertical axis is less than 10%, preferably less than 5%, more preferably less than 1%, and most preferably 0%. Furthermore, it is preferred that the top section of the dividing wall column has a substantially constant cross-sectional area along its length, and / or that the middle section of the dividing wall column has a substantially constant cross-sectional area along its length. Furthermore, it is preferred that the top section of the dividing wall distillation column have at least substantially the same cross-sectional area as the middle section, wherein substantially the same cross-sectional area means that the difference between the cross-sectional area of ​​the top section and the cross-sectional area of ​​the middle section is less than 10%, preferably less than 5%, more preferably less than 1%, and most preferably 0%. If the cross-sectional area of ​​the middle section and / or the cross-sectional area of ​​the top section are not to be constant over their length, substantially the same cross-sectional area means that the difference between the average cross-sectional area of ​​the top section and the average cross-sectional area of ​​the middle section is less than 10%, preferably less than 5%, more preferably less than 1%, and most preferably 0%. Furthermore, if the cross-sectional area of ​​the middle section and / or the cross-sectional area of ​​at least a portion of the bottom section of the dividing wall column are not to be constant over their length, the average cross-sectional area of ​​the at least a portion of the bottom section of the dividing wall column is 10% to 99%, preferably 20% to 95%, more preferably 30% to 90%, and most preferably 40% to 60% of the average cross-sectional area of ​​the middle section. For example, the (average) cross-sectional area of ​​the smaller part of the bottom section is 30% to 70% and preferably 40% to 60% of the (average) cross-sectional area of ​​the middle section of the dividing wall column. In an alternative embodiment, it is preferred that the (average) cross-sectional area of ​​the smaller part of the bottom section is 60% to 95% and preferably 70% to 85% of the (average) cross-sectional area of ​​the middle section of the dividing wall column.

[0021] As viewed from the top to the bottom of the dividing wall column, the bottom section of the dividing wall column may include a first, upper subsection having a larger cross-sectional area and a second, lower subsection having a smaller cross-sectional area. Preferably, the upper subsection has an at least substantially constant cross-sectional area over its length, and the lower subsection also has an at least substantially constant cross-sectional area over its length. Furthermore, preferably, the cross-sectional area of ​​the upper subsection of the bottom section is the same as the cross-sectional area of ​​the middle section of the dividing wall column, while the cross-sectional area of ​​the second subsection of the bottom section is 10% to 99%, preferably 20% to 95%, more preferably 30% to 90%, and most preferably 40% to 60% of the cross-sectional area of ​​the middle section.

[0022] The above embodiment can be modified so that the cross-sectional area of ​​the first upper sub-section of the bottom section is substantially the same as the cross-sectional area of ​​the middle section, which means that the difference between the cross-sectional area of ​​the first upper sub-section of the bottom section and the cross-sectional area of ​​the middle section is less than 10%, preferably less than 5% and more preferably less than 1%.

[0023] Furthermore, it is possible (though less preferred) that the cross-sectional area of ​​the first upper subsection of the bottom section varies over the length of the upper subsection, and / or the cross-sectional area of ​​the second lower subsection of the bottom section varies over the length of the lower portion, and / or the cross-sectional area of ​​the middle section varies over the length of the middle section. The cross-sectional area variation over the length of the respective (subsections) may be up to 10%, meaning that the difference between the maximum and minimum cross-sectional areas along the vertical axis of the respective (sub)sections may be up to 10%. In this case, it is preferred that the average cross-sectional area of ​​the second subsection of the bottom section is 10% to 99%, preferably 20% to 95%, more preferably 30% to 90%, and most preferably 40% to 60% of the average cross-sectional area of ​​the middle section, and that the average cross-sectional area of ​​the first subsection of the bottom section is the same as the average cross-sectional area of ​​the middle section.

[0024] According to a particularly preferred embodiment of the present invention, the bottom section of the dividing wall column, as viewed from the top to the bottom of the dividing wall column, includes a dome-shaped subsection, forming the bottom, located below the first subsection and below the second subsection. This means that, as viewed from the top to the bottom of the dividing wall column, the bottom section of the dividing wall column of this embodiment includes, and preferably consists of, a first upper subsection, a second middle subsection, and a third lower dome-shaped subsection, forming the bottom. The cross-sectional area of ​​the first upper subsection of the bottom section is the same as the cross-sectional area of ​​the middle section of the dividing wall column, while the cross-sectional area of ​​the second middle subsection of the bottom section is 10% to 99%, preferably 20% to 95%, more preferably 30% to 90%, and most preferably 40% to 60% of the cross-sectional area of ​​the middle section. Preferably, each of the middle section, the first upper subsection of the bottom section, and the second middle subsection of the bottom section has a constant diameter along its length. However, as described above, it is also possible that the cross-sectional area of ​​one, two or three of these (sub)segments varies over the length of the respective (sub)segment, wherein the cross-sectional area variation over the length of the respective (sub)segment may be up to 10%, preferably up to 5% and more preferably up to 1%, meaning that the difference between the maximum cross-sectional area and the minimum cross-sectional area along the vertical axis of the respective part of the bottom segment may be up to 10%, preferably up to 5% and more preferably up to 1%. In this case, it is preferred that the average cross-sectional area of ​​the first upper subsegment of the bottom segment is the same as the average cross-sectional area of ​​the middle segment and that the average cross-sectional area of ​​the second middle subsegment of the bottom segment is 10% to 99%, preferably 20% to 95%, more preferably 30% to 90% and most preferably 40% to 60% of the average cross-sectional area of ​​the middle segment.

[0025] According to an alternative, particularly preferred embodiment of the present invention, the bottom section of the dividing wall column, as seen in the direction from the top to the bottom of the dividing wall distillation column, includes a third intermediate subsection located below the first subsection and below the second subsection, and a dome-shaped subsection located below the third intermediate subsection, which forms the bottom of the dividing wall distillation column, wherein, as seen in the direction from the top to the bottom of the second subsection, the second subsection tapers from the cross-sectional area of ​​the first subsection to the cross-sectional area of ​​the third intermediate subsection. That means, as seen in the direction from the top to the bottom of the dividing wall column, the bottom section of the dividing wall column of this embodiment comprises, and preferably consists of, a first upper subsection, a second middle subsection, a third middle subsection, and a fourth lower dome-shaped subsection forming the bottom of the dividing wall column, wherein the cross-sectional area of ​​the first upper subsection of the bottom section is preferably the same as the cross-sectional area of ​​the middle section of the dividing wall column, while the cross-sectional area of ​​the third middle subsection of the bottom section is 10% to 99%, preferably 20% to 95%, more preferably 30% to 90%, and most preferably 40% to 60% of the cross-sectional area of ​​the middle section. Preferably, each of the first upper subsection and the third middle subsection of the bottom section has a constant diameter over its length. However, as described above, it is also possible that the cross-sectional area of ​​one, two, or three of these (sub)segments varies over the length of the respective (sub)segment, wherein the cross-sectional area variation over the length of the respective (sub)segment may be up to 10%, preferably up to 5%, and more preferably up to 1%, meaning that the difference between the maximum and minimum cross-sectional areas along the vertical axis of the respective portion of the bottom segment may be up to 10%, preferably up to 5%, and more preferably up to 1%. In this case, it is preferred that the average cross-sectional area of ​​the first upper subsegment of the bottom segment is the same as the average cross-sectional area of ​​the middle segment, and that the average cross-sectional area of ​​the third middle subsegment of the bottom segment is 10% to 99%, preferably 20% to 95%, more preferably 30% to 90%, and most preferably 40% to 60% of the average cross-sectional area of ​​the middle segment. The second middle subsegment of this embodiment preferably tapers from the cross-sectional area of ​​the first upper subsegment to the cross-sectional area of ​​the third middle subsegment, viewed from top to bottom.

[0026] In a further development of the concept of the invention, it is proposed that the dividing wall distillation column has a circular cross section, wherein the top of the top section of the dividing wall distillation column is dome-shaped, and wherein the diameter of the subsection of the top section located below the dome-shaped top is constant over the length of the top section.

[0027] Good results are particularly achieved when the inlet line for the feed and the inlet line for the extractive solvent are connected to the top section of the dividing wall column, wherein the inlet line for the extractive solvent is connected to a point of the top section above the point of connection to the feed line in the top section, wherein the inlet line for the steam is connected to the bottom section of the dividing wall column, and wherein the side outlet line is connected to the second middle subsection of the middle section of the dividing wall column.

[0028] Preferably, the side outlet line is connected to the second middle subsection of the dividing wall column.

[0029] The apparatus according to the present invention may further comprise a top condenser and a liquid-liquid separator, wherein a top outlet line is connected to the top condenser and downstream thereof to the liquid-liquid separator. In this context, "downstream thereof" means that the top condenser includes an inlet connected to the top outlet line and an outlet connected via a line to the inlet of the liquid-liquid separator. The liquid-liquid separator is preferably connected via an outlet to a water line and via another outlet to a hydrocarbon line, wherein the water line opens into the inlet of the steam generation unit, and the hydrocarbon line is divided into a discharge line and a recovery line, which is connected to the inlet of the top section of the dividing wall distillation column.

[0030] According to the present invention, the apparatus further includes a side condenser and a liquid-liquid separator. When a side outlet line is connected to the side condenser and downstream of the liquid-liquid separator, the liquid-liquid separator is connected via an outlet to a water line and preferably via another outlet to a hydrocarbon line. The water line opens into the inlet of the steam generation unit, and the hydrocarbon line preferably splits into a product line for pure styrene and a recovery line connected to the inlet of the second middle subsection of the dividing wall column. In this context, "downstream" means that the side condenser includes an inlet connected to the side outlet line and an outlet connected via a line to the inlet of the liquid-liquid separator. Alternatively, the hydrocarbon line may be solely a product line without also splitting into a recovery line. In this case, the water line may split into a line opening into the steam generation unit and a recovery line connected to the second middle subsection of the dividing wall column, so that water is recovered from the liquid-liquid separator into the dividing wall column. Alternatively still, neither the hydrocarbon line nor the water line may be split into a recovery line.In the latter case, a line for feeding a slip stream may be connected to the dividing wall column.

[0031] In a further development of the inventive concept, it is proposed that the apparatus further comprises a reboiler, wherein the bottom section comprises an outlet line and an inlet line, both being connected to a recovery line leading from the outlet line to the inlet line, wherein the recovery line is connected to the reboiler.

[0032] For example, in the above-described embodiment, each of the outlet and the inlet of the bottom section of the dividing wall distillation column is arranged at a position that is between 50% and 99% and preferably between 75% and 95% of the distance from the lowermost subsection to the uppermost subsection of the bottom section, as seen from the bottom to the top of the bottom section of the dividing wall distillation column.

[0033] In this embodiment, particularly good results are achieved when the dividing wall distillation column has a circular cross-section and the bottom section includes an upper subsection having the same diameter as the middle section and a lower subsection having a smaller diameter than the middle section, wherein each of the outlet and the inlet of the bottom section of the dividing wall distillation column is arranged in the upper subsection of the bottom section. Another subsection may be arranged between the upper subsection and the lower subsection, wherein the other subsection tapers from the cross-sectional area of ​​the upper subsection to the cross-sectional area of ​​the lower subsection.

[0034] According to a further preferred embodiment of the present invention, a (further) reboiler can be arranged in the bottom section. In this embodiment, the dividing wall distillation column preferably has a circular cross-section, and the bottom section comprises an upper subsection with the same diameter as the middle section and a lower subsection with a smaller diameter than the middle section, wherein the reboiler is arranged in the lower subsection of the bottom section. A further subsection can be arranged between the upper and lower subsections, wherein the further subsection tapers from the cross-sectional area of ​​the upper subsection to the cross-sectional area of ​​the lower subsection. This embodiment allows for particularly efficient and complete desorption of the crude mixture and requires only a minimal amount of internals, such as structured packing, in the column.

[0035] According to an alternative preferred embodiment of the present invention, a subsection of the bottom section that does not include a reboiler and is not connected to a line connected to a reboiler has a smaller cross-sectional area than the middle section of the dividing wall distillation column. In this embodiment, it is preferred that the entire bottom section does not include any reboilers. This embodiment has the following advantages, among others: it requires very small amounts of steam, reduces capital expenditure due to the omission of a reboiler, and reduces the required height of the dividing wall distillation column due to the omission of the section containing the reboiler.

[0036] In a further development of the concept of the invention, it is proposed that the steam generation unit comprises a steam generator and a solvent regenerator. When the steam generator comprises an inlet connected to a water line and an outlet for steam, the solvent regenerator comprises an inlet connected to the steam outlet of the steam generator via a line; a further inlet line connected to a solvent line, which is connected to the bottom outlet line of the dividing wall distillation column; and an outlet connected to the steam inlet line of the dividing wall distillation column.

[0037] According to a particularly preferred embodiment of the present invention, the apparatus does not comprise any liquid-liquid extractor.

[0038] In another aspect, the present invention relates to a method for separating and purifying styrene from a crude mixture comprising styrene, the method comprising the steps of: a) feeding a crude hydrocarbon composition containing styrene via an inlet line for the feed, an extractive solvent via an inlet line for the extractive solvent, and a mixture comprising the extractive solvent and water vapor via an inlet line for the steam into a dividing wall distillation column of the apparatus according to any of the preceding claims, b) distilling the crude hydrocarbon composition, the extractive solvent and water vapor in a dividing wall column, c) withdrawing a pure styrene composition via a side outlet line of the dividing wall distillation column.

[0039] During operation of the dividing wall distillation column, a mixture comprising water vapor and an extractive solvent is fed into the dividing wall distillation column via an inlet line for steam. However, for the sake of convenience of nomenclature, this inlet line is referred to herein as an inlet line for steam.

[0040] Preferably, the crude hydrocarbon composition contains 10% to 80% by weight, more preferably 30% to 60% by weight, and most preferably 40% to 50% by weight of styrene, based on 100% by weight of the crude hydrocarbon composition. For example, the crude hydrocarbon composition is a hydrocarbon C8 cut of pyrolysis gasoline obtained from steam cracking naphtha or a selectively hydrotreated hydrocarbon C8 cut, a hydrocarbon cut obtained from the (thermal or catalytic) pyrolysis of waste polystyrene, an unsaturated gasoline obtained from the (thermal or catalytic) pyrolysis of various waste plastics, etc.

[0041] According to a preferred embodiment of the present invention, the crude hydrocarbon composition contains 20% to 90% by weight, preferably 40% to 70% by weight and most preferably 50% to 60% by weight of at least one compound selected from the group consisting of xylene, toluene, ethylbenzene, C 7-9 hydrocarbons, and any mixture of two or more of the above compounds, wherein C 7-9 The hydrocarbon is preferably selected from the group consisting of alkanes, cycloalkanes, aromatic hydrocarbons, alkenes, alkynes and any mixture of two or more thereof.

[0042] Good results are particularly obtained when the extraction solvent is a sulfone, such as a cyclic or acyclic sulfone, such as sulfolane.

[0043] In a further development of the inventive concept, it is suggested that the distillation is carried out at a temperature of 40 to 140° C. and a pressure of 0.02 to 0.03 MPa and preferably at a temperature of 60 to 125° C. and a pressure of 0.005 to 0.15 MPa.

[0044] The ratio of the extraction solvent generated in the steam generation unit is preferably 80 to 95% by weight and more preferably 85 to 95% by weight based on the combination of the extraction solvent and water vapor in the mixture used in step a).

[0045] It is further preferred that the ratio of the crude hydrocarbon composition is 10 to 30% by weight, more preferably 15 to 20% by weight, based on the sum of the crude hydrocarbon composition, the extractive solvent, and the mixture comprising the extractive solvent and water vapor fed to the dividing wall distillation column in step a). BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The invention is subsequently described with the aid of the accompanying drawings, which are illustrative and non-limiting, in which: Figure 1 A schematic diagram of an apparatus for separating and purifying styrene from a crude mixture including styrene according to one embodiment of the present invention is shown.

[0047] Figure 2 A schematic diagram of an apparatus for separating and purifying styrene from a crude mixture comprising styrene according to an alternative embodiment of the present invention is shown. DETAILED DESCRIPTION

[0048] Figure 1The apparatus 10 for separating and purifying styrene from a crude mixture including styrene, shown in FIG, includes a steam generation unit 12 and a dividing wall distillation column 14. Dividing wall distillation column 14 includes a dividing wall 16 comprising a first portion 18 extending vertically downward and a second portion 20 connected to the upper end of first portion 18 and extending horizontally toward an inner wall 22 connected thereto. First portion 18 extends vertically downward from a point below the top of distillation column 14 to a point above the bottom of dividing wall distillation column 14, thereby subdividing dividing wall distillation column 14 into a top section 23 located above dividing wall 16; a bottom section 24 located below dividing wall 16; and a middle section 26 comprising a first middle subsection 28 located on one side of the first portion of the dividing wall and a second middle subsection 30 located on the opposite side of first portion 18 of dividing wall 16. Both first middle subsection 28 and second middle subsection 30 have the same cross-sectional area. The second portion 20 of the dividing wall 16 (which is connected to the upper end of the first portion 18 and extends horizontally toward the inner wall 22 connected thereto) fluid-tightly closes the entire top of the second middle subsection 30 of the dividing wall column 14. That is, the second portion 20 covers the entire top of the second middle subsection 30 of the dividing wall column 14. In contrast, the top of the first middle subsection 28 of the dividing wall column 14 is open because it is not covered at all by any element, such as the second portion 20 of the dividing wall 16. Due to the fluid-tight closure of the entire top of the second middle subsection 30 of the dividing wall column 14, during operation of the dividing wall column 14, no ascending fluid (gas and / or liquid) can exit the second middle subsection 30 upward, and no descending fluid (gas and / or liquid) can enter the second middle subsection 30 from above. Both the top and bottom of the dividing wall column 14 are dome-shaped.

[0049] As viewed from the top to the bottom of the dividing wall column 14, the bottom section 24 of the dividing wall column 14 includes a first subsection 32, a second subsection 34, a third subsection 36, and a fourth dome-shaped subsection 38 forming the bottom. As viewed along the length of the first subsection 32, the upper first subsection 32 of the bottom section 24 of the dividing wall column 14 has a constant cross-sectional area that is the same as the constant cross-sectional area of ​​the middle section 26 and the same as the cross-sectional area below the dome-shaped top of the top section 23. However, the third subsection 36 of the bottom section 24 of the dividing wall column 14 has a constant cross-sectional area that is smaller than the cross-sectional areas of the top section 23, the middle section 26, and the first subsection 32 of the bottom section 24. More specifically, the cross-sectional area of ​​the third sub-section 36 of the bottom section 24 of the dividing wall distillation column 14 is approximately 50% of the cross-sectional area of ​​the first sub-section 32, i.e., the diameter of the third sub-section 36 is approximately 70% of the diameter of the first sub-section 32. As viewed from top to bottom, the second sub-section 34 of the bottom section 24 of the dividing wall distillation column 14 tapers along its length axis from the diameter of the first sub-section 32 of the bottom section 24 to the third sub-section 36.

[0050] The dividing wall distillation column 14 further includes: an inlet line 40 for feed, which opens into the top section 23; an inlet line 42 for extractive solvent, which opens into the top section 23 at a position above the position where the inlet line 40 for feed opens into the top section 23; an inlet line 44 for steam, which is connected to a steam generating unit; a top outlet line 46; a bottom outlet line 48; and a side outlet line 50, which is connected to the second middle subsection 30 of the middle section 26 of the dividing wall distillation column 14. In addition, a top condenser 52 and a liquid-liquid separator 54 are provided, wherein the top outlet line 46 is connected to the top condenser 52 and is connected to the liquid-liquid separator 54 downstream thereof. Liquid-liquid separator 54 is connected to a water line 56 and to a hydrocarbon line 58, wherein water line 56 opens into steam generation unit 12, and hydrocarbon line 58 is divided into a discharge line 60 and a recovery line 62, which is connected to top section 23 of dividing wall distillation column 14. Furthermore, a side condenser 64 and another liquid-liquid separator 66 are provided, wherein side outlet line 50 is connected to side condenser 64 and is connected downstream to liquid-liquid separator 66. Furthermore, liquid-liquid separator 66 is connected to a water line 68 and to a hydrocarbon line 70, wherein water line 68 opens into steam generation unit 12, and hydrocarbon line 70 is divided into a product line 72 for pure styrene and a recovery line 74, which is connected to second middle subsection 30 of middle section 26 of dividing wall distillation column 14. Furthermore, the apparatus 10 comprises a first reboiler 76, wherein the first subsection 32 of the bottom section 24 comprises an outlet line 78 and an inlet line 80, both of which are connected to a recovery line 82 leading from the outlet line 78 to the inlet line 80, wherein the recovery line 82 is connected to the first reboiler 76. A second reboiler 84 is arranged in the third subsection 36 of the bottom section 24 of the dividing wall column 14. This second reboiler 84 allows particularly efficient and complete desorption of the crude mixture and requires only a minimum amount of internals, such as structured packing, in the dividing wall column 14.

[0051] Finally, steam generation unit 12 includes a steam generator 86 and a solvent regenerator 88. Steam generator 86 includes an inlet 90 connected to a water line 92 into which water lines 56 and 68 flow, and a steam outlet line 94. Solvent regenerator 88 includes an inlet 96 connected to steam outlet line 94 of steam generator 86, further includes an inlet line 98 connected to solvent line 98 connected to bottom outlet line 48 of dividing wall column 14, and further includes an outlet 100 connected to steam inlet line 44 of dividing wall column 14.

[0052] During operation, a crude mixture containing styrene (e.g., a C8 fraction feed) is fed into the dividing wall distillation column 14 via inlet line 40, while an extractive solvent is fed via inlet line 42, and a mixture of (water) steam and extractive solvent is fed into the dividing wall distillation column 14 via inlet line 44. While the top section and the first middle subsection 28 function as the extractive distillation section during distillation, the second middle subsection 30 functions as the rectifying section during distillation, and the bottom section 24 functions as the solvent desorption section. The overhead stream, which includes small amounts of non-aromatic hydrocarbons, toluene, mixed xylenes, and styrene, as well as large amounts of water and ethylbenzene, is directed through an overhead condenser 52 and a liquid-liquid separator 54, where the overhead stream is condensed and separated into an aqueous stream and a hydrocarbon stream. While the aqueous stream is directed to steam generator 86 via lines 56 and 92, the hydrocarbon stream is partially recovered to dividing wall column 14 via recovery line 62, with the remainder being withdrawn from the plant, for example, as a C8 raffinate, via line 60. Regenerated extractive solvent is withdrawn via bottom line 48 and partially directed to top section 23 of dividing wall column 14 via inlet line 42, with the remainder being directed to the solvent regenerator via solvent line 98. A purified styrene stream is withdrawn from second middle subsection 30 of dividing wall column 14 via side outlet line 50, condensed in side condenser 64, and separated into an aqueous stream and a hydrocarbon stream in liquid-liquid separator 66. While the aqueous stream is directed to steam generator 86 via lines 68 and 92, the hydrocarbon stream is partially recovered to dividing wall column 14 via recovery line 74, with the remainder being withdrawn from the plant via product line 72 as a pure styrene stream. The water is evaporated into steam in the steam generator 86 and then mixed with the solvent in the solvent regenerator 88 , after which the resulting mixture of water vapor and solvent is fed via line 44 into the bottom section 24 of the dividing wall column 14 .

[0053] Figure 1 Detailed Description of the Preferred Embodiments 10 shows an apparatus 10 for separating and purifying styrene from a crude mixture comprising styrene.

[0054] Reference numerals 10 Equipment 12 Steam generating unit 14 Dividing Wall Distillation Column 16 partition wall 18 The first part of the partition wall 20 Second part of the partition wall 22 inner wall 23 Top section of a dividing wall distillation column 24 Bottom section of a dividing wall distillation column 26 The middle section of the dividing wall distillation column 28 First middle subsection 30 Second middle subsection 32 First sub-segment 34 Second subsection 36 Third subsection 38 Fourth subsection 40 Inlet line for feed 42 Inlet line for extraction solvent 44 Steam inlet line 46 Tower top outlet pipeline 48 bottom outlet pipeline 50 side outlet pipeline 52 Top condenser 54 Liquid-Liquid Separator 56 Water Pipeline 58 Hydrocarbon Pipeline 60 discharge line 62 Recovery pipeline 64 side condenser 66 Liquid-Liquid Separator 68 Water Pipeline 70 Hydrocarbon Pipeline 72 Pure styrene product pipeline 74 Recovery pipeline 76 First Reboiler 78 export pipeline 80 Inlet pipeline 82 Recovery pipeline 84 Second reboiler 86 Steam Generator 88 Solvent Regenerator 90 Steam generator inlet 92 water pipeline 94 Steam export pipeline 96 Inlet of solvent regenerator 98 solvent lines 100 Outlet of solvent regenerator.

Claims

1. A device (10) particularly for separating and purifying styrene from a crude mixture comprising styrene, wherein: The apparatus (10) comprises a steam generating unit (12) and a dividing wall distillation column (14), wherein the dividing wall distillation column (14) comprises a dividing wall (16), the dividing wall comprising a first portion (18) extending at least substantially vertically downward from a point below the top of the distillation column (14) to a point above the bottom of the dividing wall distillation column (14) so ​​as to subdivide the dividing wall distillation column (14) into: a top section (23) located above the dividing wall (16); a bottom section (24) below the partition wall (16); and a middle section (26) comprising a first middle sub-section (28) located on one side of the first portion (18) of the partition wall (16) and a second middle sub-section (30) located on an opposite side of the first portion (18) of the partition wall (16), wherein the partition wall (16) further comprises a second section (20) connected to an upper portion of the first portion (18) of the partition wall and extending to the second middle sub-section (30) to the inner wall of the dividing wall distillation column (14), wherein at least a portion of the bottom section (24) extending over at least 10% of the height of the dividing wall distillation column (14) has a smaller cross-sectional area than the middle section (26) of the dividing wall distillation column (14), wherein the dividing wall distillation column (14) further comprises an inlet line (40) for feed, an inlet line (42) for extractive solvent, an inlet line (44) for steam connected to the steam generation unit (12), and a tower top outlet line (46). ), a bottom outlet line (48), and a side outlet line (50) connected to the second middle sub-section (30) of the dividing wall distillation column (14), wherein the device (10) further includes a side condenser (64) and a liquid-liquid separator (66), wherein the side outlet line (50) is connected to the side condenser (64) and connected to the liquid-liquid separator (66) downstream thereof, wherein the liquid-liquid separator (66) is connected to a water line (68) entering the steam generating unit (12).

2. The device (10) according to claim 1, wherein The angle between the first portion (18) of the dividing wall (16) and the length axis of the top dividing wall distillation column (14) is at most 20°, preferably at most 10°, more preferably at most 5° and most preferably 0°, wherein, as seen from the bottom to the top of the dividing wall distillation column (14), the first portion (18) of the dividing wall (16) extends from a point located at 10% to 45% of the distance from the bottom to the top of the dividing wall distillation column (14) to a point located at 50% to 90% of the distance from the bottom to the top of the dividing wall distillation column (14), and preferably from a point located at 25% to 40% of the distance from the bottom to the top of the dividing wall distillation column (14) to a point located at 50% to 75% of the distance from the bottom to the top of the dividing wall distillation column (14).

3. The device (10) according to claim 1 or 2, wherein One of the first middle sub-section (28) and the second middle sub-section (30) covers at least 30%, more preferably at least 40%, still more preferably at least 45% and most preferably 50% of the total cross-sectional area of ​​the middle section (26) of the dividing wall column (14), while the other of the first middle sub-section (28) and the second middle sub-section (30) covers the remainder of 100% of the total cross-sectional area of ​​the middle section (26) of the dividing wall column (14).

4. The device (10) according to any one of the preceding claims, wherein The second portion (20) of the dividing wall (16) is connected to the upper part of the first portion (18) of the dividing wall (16), extends into the second middle subsection (30) as far as the inner wall of the dividing wall distillation column (14), and is connected to the inner wall of the dividing wall distillation column (14) so ​​as to fluid-tightly close the top of the second middle subsection (30) of the dividing wall distillation column (14), wherein the second portion (20) of the dividing wall (16) extends at least essentially horizontally to the inner wall of the dividing wall distillation column (14), wherein the angle between the second portion (20) of the dividing wall (16) and the cross-sectional plane of the top dividing wall distillation column (14) is at most 20°, preferably at most 10°, more preferably at most 5° and most preferably 0°.

5. The device (10) according to any one of the preceding claims, wherein The cross-sectional area of ​​the at least a portion of the bottom section (24) of the dividing wall column (14) is 10% to 99%, preferably 20% to 95%, more preferably 30% to 90% and most preferably 40% to 60% of the cross-sectional area of ​​the middle section (26).

6. The device (10) according to any one of the preceding claims, wherein As viewed from the top to the bottom of the dividing wall distillation column (14), the bottom section (24) of the dividing wall distillation column (14) includes a first subsection (32) and a second subsection (34), wherein the first subsection (32) is located above the second subsection (34), wherein the cross-sectional area of ​​the upper subsection (32) of the bottom section is the same as the cross-sectional area of ​​the middle section (26) of the dividing wall distillation column (14), and the second subsection of the bottom section (24) is The cross-sectional area of ​​the section (34) is 10% to 99%, preferably 20% to 95%, more preferably 30% to 90% and most preferably 40% to 60% of the cross-sectional area of ​​the middle section (26), wherein, preferably, as seen in the direction from the top to the bottom of the dividing wall distillation column (14), the bottom section (24) of the dividing wall column (14) comprises a dome-shaped subsection forming the bottom, located below the first subsection (32) and below the second subsection (34).

7. The device (10) according to any one of claims 1 to 5, wherein As viewed from the top to the bottom of the dividing wall distillation column (14), the bottom section (24) of the dividing wall distillation column (14) includes a first upper subsection (32), a second middle subsection (32), a third middle subsection (36), and a dome-shaped subsection (38) located below the third middle subsection (36) and forming the bottom of the dividing wall distillation column (14), wherein the cross-sectional area of ​​the first upper subsection (32) of the bottom section (24) is the same as the cross-sectional area of ​​the middle section (26) of the dividing wall distillation column (14), and wherein the cross-sectional area of ​​the third middle subsection (36) of the bottom section (24) is 1 / 2 of the cross-sectional area of ​​the middle section (26). 0% to 99%, preferably 20% to 95%, more preferably 30% to 90% and most preferably 40% to 60%, and wherein, seen in a direction from the top to the bottom of the second middle sub-section (34), the second middle sub-section (34) tapers from the cross-sectional area of ​​the first upper sub-section (32) to the cross-sectional area of ​​the third middle sub-section (36), wherein, preferably, the dividing wall distillation column (14) has a circular cross-section, wherein the top of the top section (23) of the dividing wall distillation column (14) is dome-shaped, and wherein the diameter of the sub-section of the top section (23) located below the dome-shaped top is constant over the length of the top section (23).

8. The device (10) according to any one of the preceding claims, wherein The feed inlet line (40) and the extractive solvent inlet line (42) are connected to the top section (23) of the dividing wall distillation column (14), wherein the extractive solvent inlet line (42) is connected to a position of the top section (23) above the position of the top section (23) connected to the feed line (40), wherein the steam inlet line (44) is connected to the bottom section (24) of the dividing wall distillation column (14), and wherein the side outlet line (50) is connected to the middle section (26) of the dividing wall distillation column (14).

9. The apparatus (10) according to any one of the preceding claims, further comprising a top condenser (52) and a liquid-liquid separator (54), wherein The top outlet pipeline (50) is connected to the top condenser (52) and is connected to the liquid-liquid separator (54) downstream thereof, wherein the liquid-liquid separator (54) is connected to a water pipeline (56) and to a hydrocarbon pipeline (58), wherein the water pipeline (56) flows into the steam generation unit (12), and the hydrocarbon pipeline (58) is divided into a discharge pipeline (60) and a recovery pipeline (62), and the recovery pipeline is connected to the top section (23) of the dividing wall distillation column (14).

10. The device (10) according to any one of the preceding claims, wherein The liquid-liquid separator (66) connected to the side outlet line (50) is connected to a water line (68) and to a hydrocarbon line (70), wherein the hydrocarbon line (70) is divided into a product line (72) and a recovery line (74), and the recovery line is connected to the second middle subsection (30) of the dividing wall distillation column (14).

11. The apparatus (10) according to any one of the preceding claims, further comprising a reboiler (76), wherein The bottom section (24) includes an outlet line (78) and an inlet line (80), both of which are connected to a recovery line (82) leading from the outlet line (78) to the inlet line (80), wherein the recovery line (80) is connected to the reboiler (76).

12. The device (10) according to any one of the preceding claims, wherein The reboiler (84) is arranged in the bottom section (24), wherein the dividing wall distillation column (14) has a circular cross-section, and the bottom section (24) includes an upper subsection (32) having the same diameter as the middle section (26) and a lower subsection (34) having a smaller diameter than the middle section (26), wherein the reboiler (84) is arranged in the lower subsection (34) of the bottom section (24).

13. The device (10) according to any one of claims 1 to 11, wherein The subsection (34) of the bottom section (24) does not include a reboiler (76, 84) and is not connected to a line connected to the reboiler (76, 84), and has a smaller cross-sectional area than the middle section (26) of the dividing wall distillation column (14).

14. The device (10) according to any one of the preceding claims, wherein The steam generating unit (12) comprises a steam generator (86) and a solvent regenerator (88), wherein the steam generator (86) comprises an inlet (90) connected to a water line (92) and an outlet (94) for steam, wherein the solvent regenerator (88) comprises an inlet (96) connected to the outlet (94) for steam of the steam generator (86) via a line; comprises another inlet line connected to a solvent line (98), the solvent line being connected to the bottom outlet line (48) of the dividing wall distillation column (14); and comprises an outlet (100) connected to the inlet line (44) for steam of the dividing wall distillation column (14).

15. A method for separating and purifying styrene from a crude mixture comprising styrene, the method comprising the steps of: a) feeding a crude hydrocarbon composition containing styrene via the feed inlet line (40), an extractive solvent via the extractive solvent inlet line (42), and a mixture comprising extractive solvent and water vapor via the steam inlet line (44) into a dividing wall distillation column (14) of the apparatus (10) according to any of the preceding claims, b) distilling the crude hydrocarbon composition, the extraction solvent and the water vapor in the dividing wall column (14), c) removing a pure styrene composition via a side outlet line (50) of the dividing wall distillation column (14).

16. The method according to claim 15, wherein The crude hydrocarbon composition contains 10 to 80% by weight, preferably 30 to 60% by weight, and more preferably 40 to 50% by weight, of styrene, and 20 to 90% by weight, preferably 40 to 70% by weight, and most preferably 50 to 60% by weight, of at least one compound selected from the group consisting of xylene, toluene, ethylbenzene, C 7-9 hydrocarbons, and any mixture of two or more of the above compounds, wherein the C 7-9 The hydrocarbon is preferably selected from the group consisting of alkanes, cycloalkanes, aromatic hydrocarbons, alkenes, alkynes and any mixture of two or more thereof.

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