JPWO2018143041A1 - Method and apparatus for separating and collecting isoprene - Google Patents

Abstract

A method for separating and recovering isoprene that makes it possible to reduce the amount of isoprene polymer produced when isoprene is separated and recovered from a mixed fluid containing isoprene. The method for separating and recovering isoprene according to the present invention is a method for separating and recovering isoprene from a mixed fluid containing isoprene, wherein the mixed fluid is subjected to extractive distillation and is soluble in the extraction solvent used for the extractive distillation. Is an extractive distillation step for obtaining a fraction containing impurities lower than isoprene and a fraction containing crude isoprene, and a fraction containing impurities having a higher boiling point than isoprene by fractional distillation of the fraction containing crude isoprene. And a fractional distillation step for obtaining a fraction containing impurities having a boiling point lower than that of isoprene and a fraction containing isoprene of high purity.

Description

  The present invention relates to a method and apparatus for separating and recovering isoprene, and in particular, isoprene that makes it possible to reduce the amount of isoprene polymer produced when isoprene is separated and recovered from a mixed fluid containing isoprene. The present invention relates to a separation and recovery method and a separation and recovery apparatus.

  Conventionally, a method using extractive distillation is known as a method for separating and recovering high-purity isoprene from a mixed fluid such as a C5 fraction produced as a by-product when ethylene is produced by steam cracking of hydrocarbons or other high-temperature treatment. ing.

  Specifically, as a method for separating and recovering isoprene from a mixed fluid such as a C5 fraction using extractive distillation, for example, by separating impurities having a boiling point close to that of isoprene such as pentane and pentene from a mixed fluid containing isoprene. A method of separating and recovering high-purity isoprene is used (for example, see Patent Document 1).

  Here, in the method for separating and recovering isoprene using extractive distillation, impurities having a lower boiling point than isoprene such as 1,4-pentadiene and 2-butyne, which are components that inhibit polymerization reaction such as isoprene synthetic rubber, and piperylene It is possible to separate and remove impurities having a boiling point higher than that of isoprene.

JP 47-41323 A

  However, the method for separating and recovering isoprene using extractive distillation has not been able to suppress the production of a polymer of isoprene, which can cause equipment contamination.

  Accordingly, the present invention provides an isoprene separation and recovery method and an isoprene separation and recovery device that can reduce the amount of isoprene polymer produced when isoprene is separated and recovered from a mixed fluid containing isoprene. For the purpose.

An object of the present invention is to advantageously solve the above-mentioned problems, and the method of separating and recovering isoprene of the present invention is a method of separating and recovering isoprene in which isoprene is separated and recovered from a mixed fluid containing isoprene, Extractive distillation of the mixed fluid to obtain a fraction containing impurities having lower solubility in the extraction solvent used in the extractive distillation than isoprene; and a fraction containing crude isoprene; and the crude isoprene A fractional distillation step of fractionating a fraction containing the fraction to obtain a fraction containing impurities having a boiling point higher than that of isoprene, a fraction containing impurities having a boiling point lower than that of isoprene, and a fraction containing isoprene having a high purity; , Including. Thus, by fractionally distilling the fraction containing crude isoprene, the thermal load is reduced, and the amount of isoprene polymer produced when separating and recovering isoprene from the mixed fluid containing isoprene is reduced. Can do. Therefore, it is possible to reduce the frequency of polymer cleaning that needs to be performed while the operation of the isoprene separation and recovery apparatus is stopped.
In the present invention, “high purity isoprene” means “isoprene having a higher concentration than isoprene concentration in crude isoprene”. Here, the “isoprene concentration” can be measured using gas chromatography.
Furthermore, in the present invention, “division distillation” refers to dividing a product to be distilled into three or more (preferably three) fractions in a single distillation operation. For example, a vertical division distillation column or the like is used. Can be implemented.

  Here, in the method for separating and recovering isoprene of the present invention, the extraction solvent in the extractive distillation step is preferably an amide compound, and more preferably dimethylformamide. By using an amide compound, particularly dimethylformamide, as the extraction solvent, extractive distillation can be performed efficiently.

  Further, the method for separating and recovering isoprene of the present invention further comprises subjecting the fraction containing the high-purity isoprene to extractive distillation, and a fraction containing impurities having higher solubility in the extraction solvent used in the extractive distillation than isoprene. Furthermore, it is preferable to further include a second extractive distillation step for obtaining a fraction containing isoprene having a higher purity. If the fraction containing the high-purity isoprene is further subjected to extractive distillation (second extractive distillation), a readily soluble substance (an impurity having higher solubility in the extraction solvent than that of isoprene) is separated to obtain a higher-purity isoprene. be able to. Further, if the extractive distillation (second extractive distillation) is further performed after the fractional distillation, the easily soluble substance cyclopentadiene is separated in advance by the fractional distillation, so that even higher purity isoprene can be obtained efficiently.

  Here, in the method for separating and recovering isoprene of the present invention, the extraction solvent in the second extractive distillation step is preferably an amide compound, and more preferably dimethylformamide. By using an amide compound, particularly dimethylformamide, as the extraction solvent, extractive distillation can be performed efficiently.

  In the method for separating and recovering isoprene of the present invention, it is preferable that the isoprene concentration of a fraction (mixed fluid) containing impurities having a boiling point lower than that of the isoprene is 5% by mass or more and 90% by mass or less. If the isoprene concentration of the mixed fluid is 5% by mass or more and 90% by mass or less, high-purity isoprene can be efficiently separated and recovered from the mixed fluid.

  In the method for separating and recovering isoprene of the present invention, it is preferable that in the fractional distillation step, fractional distillation is performed in the presence of a polymerization inhibitor of 1 to 100 mass ppm with respect to the crude isoprene. If the fractional distillation is performed in the presence of the above-described amount of the polymerization inhibitor, the polymerization reaction during the fractional distillation can be suppressed, and the occurrence of dirt and clogging can be prevented in the fractional distillation column that performs the fractional distillation.

In the method for separating and recovering isoprene of the present invention, it is preferable that the fractional distillation in the fractional distillation step is performed in a fractional distillation column, and the polymerization inhibitor is supplied from the vertical upper part of the fractional distillation column. If the polymerization inhibitor is supplied from the upper part in the vertical direction of the fractional distillation column, the polymerization inhibitor can be spread over the entire fractional distillation column.
In the present invention, “vertical upper portion of the fractional distillation column” means “upper portion of 70% to 100% of the vertical height of the fractional distillation column”.

  In the method for separating and recovering isoprene of the present invention, the fraction containing the high-purity isoprene is preferably a gas. If the fraction containing the high-purity isoprene is a gas, the high-purity isoprene can be prevented from containing a polymerization inhibitor. Therefore, high-purity isoprene can be advantageously used for polymerization for obtaining polyisoprene and the like.

  Moreover, it is preferable that the method for separating and recovering isoprene of the present invention further includes a step of removing the polymerization inhibitor from the fraction containing the high-purity isoprene. If the polymerization inhibitor is removed from the fraction containing the high-purity isoprene, the high-purity isoprene can be advantageously used for polymerization for obtaining polyisoprene or the like.

  In addition, the present invention is intended to advantageously solve the above problems, and the isoprene separation and recovery device of the present invention has a supply port for supplying a mixed fluid containing isoprene, and the mixing An extractive distillation section for subjecting the fluid to extractive distillation to obtain a fraction containing impurities having lower solubility in the extraction solvent used in the extractive distillation than isoprene; and a fraction containing crude isoprene; and a fraction containing the crude isoprene. A fraction containing an impurity having a boiling point higher than that of isoprene, and a fraction containing impurities having a lower boiling point than that of isoprene. And a fractional distillation section for obtaining a fraction containing high-purity isoprene. By fractionally distilling the fraction containing crude isoprene, the heat load can be reduced, and the amount of isoprene polymer produced when separating and recovering isoprene from the mixed fluid containing isoprene can be reduced. Therefore, it is possible to reduce the frequency of polymer cleaning that needs to be performed while the operation of the isoprene separation and recovery apparatus is stopped.

  Here, the apparatus for separating and recovering isoprene of the present invention has a supply port for supplying the fraction containing the high-purity isoprene, further extractively distilling the fraction containing the high-purity isoprene, It is preferable to further include a second extractive distillation section for obtaining a fraction containing impurities having higher solubility in the extraction solvent used for the extractive distillation than that of isoprene and a fraction containing isoprene having a higher purity. If the fraction containing high-purity isoprene is further subjected to extractive distillation, it is possible to efficiently separate easily soluble substances (impurities having higher solubility in the extraction solvent than isoprene), and to produce even higher-purity isoprene.

  ADVANTAGE OF THE INVENTION According to this invention, the production amount of the polymer of isoprene produced | generated when isoprene is isolate | separated and collect | recovered from the fluid mixture containing isoprene can be reduced.

It is a figure which shows schematic structure of an example of the separation-and-recovery apparatus of isoprene according to this invention. It is a figure which shows schematic structure of an example of the separation-and-recovery apparatus of the conventional isoprene.

Hereinafter, embodiments of the present invention will be described in detail.
Here, the method for separating and collecting isoprene of the present invention can be used when separating and collecting isoprene from a mixed fluid raw material containing isoprene such as a C5 fraction. Further, the isoprene separation and recovery apparatus of the present invention can be suitably used, for example, when isoprene is separated and recovered using the isoprene separation and recovery method of the present invention.

(Isoprene separation and recovery method)
The method for separating and collecting isoprene of the present invention is a method for separating and collecting isoprene from a mixed fluid containing isoprene. The method for separating and recovering isoprene according to the present invention includes extractive distillation of a mixed fluid containing isoprene, a fraction containing impurities whose solubility in the extraction solvent used for the extractive distillation is lower than that of isoprene, and crude isoprene. A fraction containing an isoprene, a fraction containing crude isoprene, a fraction containing crude isoprene, optionally in the presence of a polymerization inhibitor, fractionally distilled, and a fraction containing impurities having a boiling point higher than that of isoprene, and isoprene And a step (a fractional distillation step) of obtaining a fraction containing impurities having a lower boiling point and a fraction containing high-purity isoprene, and optionally further subjecting the fraction containing high-purity isoprene to extractive distillation. Thus, a step (second extractive distillation step) for obtaining a fraction containing impurities having higher solubility in the extraction solvent used in the extractive distillation than that of isoprene, and a fraction containing higher purity isoprene, and a high purity I Further comprising a step (removal step) of removing the polymerization inhibitor used in division distilled from fraction containing Puren.

  In the method for separating and recovering isoprene according to the present invention, the fraction of crude isoprene is subjected to fractional distillation to reduce the thermal load and reduce the isoprene generated when the isoprene is separated and recovered from the mixed fluid containing isoprene. The amount of coalescence can be reduced. Therefore, it is possible to reduce the frequency of polymer cleaning that needs to be performed while the operation of the isoprene separation and recovery apparatus is stopped.

  In the fractional distillation step of the method for separating and recovering isoprene of the present invention, the polymerization reaction during fractional distillation can be suppressed by fractional distillation in the presence of a polymerization inhibitor. In general, since the operating pressure and temperature at the time of carrying out the fractional distillation are relatively high compared to the ordinary distillation, a polymerization reaction tends to occur during the fractional distillation. However, if the fractional distillation is performed in the presence of a polymerization inhibitor, the polymerization reaction during the fractional distillation can be suppressed, and contamination and clogging can be prevented from occurring in an apparatus such as a fractional distillation tower that performs the fractional distillation. .

  In the method for separating and recovering isoprene of the present invention, the polymerization inhibitor used in the fractional distillation is removed from the fraction containing high-purity isoprene, thereby preventing the high-purity isoprene from containing the polymerization inhibitor. Can do. Specifically, when a polymerization inhibitor is contained in high-purity isoprene, polymerization is hindered even if it is attempted to polymerize high-purity isoprene. However, if the polymerization inhibitor used in the fractional distillation is removed, it is possible to prevent the polymerization from being hindered when polymerizing high-purity isoprene.

  Further, in the method for separating and recovering isoprene of the present invention, in the fractional distillation step, a fraction containing high-purity isoprene is extracted with a gas, thereby preventing the high-purity isoprene from containing a polymerization inhibitor. . Specifically, when a polymerization inhibitor is contained in high-purity isoprene, polymerization is hindered even if it is attempted to polymerize high-purity isoprene. However, if a fraction containing high-purity isoprene is withdrawn as a gas, the high-purity isoprene is prevented from containing a polymerization inhibitor, and polymerization is inhibited when high-purity isoprene polymerization is attempted. Can be prevented.

<Mixed fluid containing isoprene>
The mixed fluid preferably contains 1% by mass or more of isoprene. When the content of isoprene in the mixed fluid is 1% by mass or more, it is possible to efficiently separate and recover isoprene from the mixed fluid.
Normally, the content of isoprene in the mixed fluid is 5% by mass or more and 30% by mass or less. The mixed fluid contains n-pentane, 1,4-pentadiene, 2-butyne, piperylene, cyclopentadiene and the like in addition to isoprene.

<Extraction distillation process>
In the extractive distillation step of the mixed fluid separation and recovery method of the present invention, the mixed fluid containing the mixed fluid is subjected to extractive distillation to separate impurities different from isoprene in the extractive solvent used for the extractive distillation from the mixed fluid. To obtain a fraction containing crude isoprene.

Extractive distillation
FIG. 1 is a diagram showing a schematic configuration of an example of an isoprene separation / recovery apparatus that can carry out the isoprene separation / recovery method according to the present invention.
In FIG. 1, the extractive distillation unit 10 extracts and distills a mixed fluid raw material containing isoprene, such as a C5 fraction, and separates it into a fraction (C) and an extract (D). And a stripping tower 13 for removing the solvent from the extract (D).

  In the first extractive distillation column 12, the solvent is supplied to the upper stage (upper vertical direction) from the supply stage of the mixed fluid raw material containing isoprene such as the C5 fraction, and the solvent is extracted and distilled from the isoprene. A fraction (C) containing a slightly soluble n-pentane (boiling point: 36.1 ° C.), and the like, are distilled from the top of the tower, and isoprene, 1,4-pentadiene, 2-butyne, piperylene, cyclopentadiene, The extract (D) containing etc. is taken out from the tower bottom.

  As the solvent supplied to the first extractive distillation column 12, a known solvent used for extractive distillation of the C5 fraction such as the solvent described in International Publication No. 99/051552 is used. it can. Among these, amide compounds are preferable, and dimethylformamide is more preferable. By using an amide compound, particularly dimethylformamide, as the extraction solvent, extractive distillation can be performed efficiently.

  In the stripping tower 13, the solvent is taken out from the bottom of the tower, and the fraction (X) containing isoprene, 1,4-pentadiene, 2-butyne, piperylene, cyclopentadiene, etc. (including crude isoprene) from the top of the tower. Distillate). In addition, the solvent collect | recovered by the stripping tower 13 can be reused arbitrarily in the 1st extractive distillation tower 12 or the 2nd extractive distillation tower 15 mentioned later.

<Division distillation process>
In the fractional distillation step of the method for separating and recovering isoprene of the present invention, fractions containing crude isoprene are fractionally distilled to separate impurities having higher boiling points than isoprene and impurities having lower boiling points than isoprene from fractions containing crude isoprene. Thus, a fraction containing high-purity isoprene is obtained. Thus, by fractionally distilling the fraction containing crude isoprene, the heat load is reduced compared to the case where the removal of the high boiling point component by distillation and the removal of the low boiling point component by distillation are performed in two stages. Thus, the amount of isoprene polymer produced when separating and recovering isoprene from the mixed fluid containing isoprene can be reduced. Therefore, it is possible to reduce the frequency of polymer cleaning that needs to be performed while the operation of the isoprene separation and recovery apparatus is stopped.

[Division distillation]
Here, in the fractional distillation, for example, as described in JP-A-2006-524522, a fractional distillation tower is used to remove a high-boiling component (a fraction containing impurities having a boiling point higher than that of isoprene) from the bottom of the tower. A fraction containing impurities with a higher boiling point than isoprene is discharged by discharging the medium-boiling components from the central region of the tower and discharging a low-boiling component (a fraction containing impurities having a lower boiling point than isoprene) from the top of the tower. And a fraction containing impurities having a boiling point lower than that of isoprene and a fraction containing high-purity isoprene can be obtained.
The isoprene concentration of the fraction containing impurities having a boiling point lower than that of isoprene, that is, the isoprene concentration on the top side of the fractional distillation column 21 is preferably 5% by mass or more and 90% by mass or less, and preferably 10% by mass or more. More preferably, it is 70 mass% or less. Thus, if the isoprene concentration of the fraction containing impurities having a lower boiling point than isoprene is 5% by mass or more and 90% by mass or less, a high boiling point component (impurities having a higher boiling point than isoprene) or a low boiling point component (from isoprene) In addition, it is possible to efficiently separate the high-boiling component and the low-boiling component by preventing the mixing of the low-boiling impurity) into the middle-boiling component.
In general, the concentration of isoprene in the fraction containing impurities having a boiling point lower than that of isoprene is 15% by mass or more and 25% by mass or less.
The fraction containing impurities having a boiling point higher than that of isoprene preferably contains 3% by mass or more of piperylene, which is a useful component.

-Division distillation tower-
Here, as the fractional distillation column, for example, as described in JP-A-2006-524522, for example, a vertical division type column having division walls arranged in the length direction, and the like can be mentioned. The dividing wall divides the interior of the column into, for example, a feed section (left side of the dividing wall), a removal section (right side of the dividing wall), an upper binding column section (rectification section), and a lower binding column section (stripping section). To do.
The feed port (feed inlet) for feeding the fraction containing the crude isoprene that is subject to the fractional distillation is generally between the central region of the feed section (ie, between the upper and lower regions of the feed section). ). One or more supply ports (feed inlets) may be further provided in the central region of the feed section.
Also, typically, in the removal section, one or more sideflow outlets are disposed in the central region of the removal section (ie, between the upper and lower regions of the removal section). One or more side flow outlets may be further provided in the central region of the removal section.
By using the above-mentioned fractional distillation column, the cost reduction of about 30% and the substance to be treated are compared with the case of direct connection between the conventional high boiling distillation column and the low boiling distillation column (for example, in the case of FIG. 2 described later). The residence time can be shortened, and the mixed fluid can be divided and distilled at a low heat load (the high-boiling component and the low-boiling component are separated and removed from the fraction containing the crude isoprene).

Hereinafter, the case of performing fractional distillation in a fractional distillation section composed of a fractional distillation column will be described with reference to the drawings.
In FIG. 1, the fractional distillation unit 20 includes a fractional distillation column 21 that fractionally distills a fraction (X) containing crude isoprene distilled from the top of the stripping tower 13.
The fractional distillation column 21 is, for example, 1,4-pentadiene (boiling point: 26 ° C.), 2-butyne (boiling point: 27 ° C.), etc. contained in the fraction (X) obtained in the extractive distillation section 10. A fraction (E) containing low-boiling impurities is distilled from the top of the column, and a fraction (F) containing high-boiling impurities such as piperylene (boiling point: 42 ° C.) is taken out from the bottom of the column, and isoprene ( A high-purity isoprene is distilled from the central region of the column as a fraction (G) enriched in boiling point: 34.1 ° C.).

  When fractional distillation is performed, generally, the operating pressure and temperature at the time of performing fractional distillation are relatively higher than those of ordinary distillation, so that a polymerization reaction tends to occur during the fractional distillation. Therefore, although a polymerization reaction is likely to occur in the fractional distillation column 21, by performing the fractional distillation in the presence of a polymerization inhibitor, the polymerization reaction during the fractional distillation is suppressed, so that the fractional distillation column 21 is contaminated or clogged. Can be prevented.

-Polymerization inhibitor-
Specific examples of the polymerization inhibitor are not particularly limited, and, for example, 4-tertiary butylcatechol (TBC), diethylhydroxyamine (DEHA), and the like can be used.

  The amount of the polymerization inhibitor to be present in the fractional distillation is not particularly limited, but from the viewpoint of suppressing the polymerization reaction during the fractional distillation, it is preferably 1 ppm by mass or more based on the crude isoprene, and has a high purity. From the viewpoint of reducing the content of the polymerization inhibitor in isoprene, it is preferably 100 ppm by mass or less with respect to parts by mass of the crude isoprene.

  The supply place of the polymerization inhibitor is not particularly limited as long as the polymerization inhibitor is present in the fractional distillation, and the polymerization inhibitor may be directly supplied to the fractional distillation tower 21 or the polymerization inhibitor may be divided. You may supply to piping just before the distillation column 21. FIG. Here, the polymerization inhibitor is supplied to the fractional distillation column 21 by supplying the polymerization inhibitor at the upper side in the upper stage (upper vertical direction) of the fraction (X) containing the crude isoprene in the fractional distillation tower 21. Can be spread throughout.

  In the fractional distillation section 20, it is possible to prevent the polymerization inhibitor from being contained in the high-purity isoprene by extracting the fraction containing the high-purity isoprene from the fractional distillation column 21 with a gas. Specifically, when a polymerization inhibitor is contained in high-purity isoprene, polymerization is hindered even if it is attempted to polymerize high-purity isoprene. However, if a fraction containing high-purity isoprene is withdrawn from the fractional distillation column 21 in the form of a gas, polymerization is prevented when the high-purity isoprene is polymerized by preventing the high-purity isoprene from containing a polymerization inhibitor. Can be prevented.

<Second extractive distillation process>
In the method for separating and recovering isoprene of the present invention, it is preferable that the fraction containing high-purity isoprene is further subjected to extractive distillation (second extractive distillation). In this way, a fraction containing higher purity isoprene can be obtained by further extractive distillation (second extraction distillation) of the fraction containing high purity isoprene.
Here, regarding cyclopentadiene, which is a substance that is easily soluble in the extraction solvent, the concentration of cyclopentadiene in the fraction containing high-purity isoprene is reduced in advance in the fractional distillation section, so that even higher-purity isoprene can be efficiently obtained in the second extraction distillation. Can be generated.

[Second extractive distillation]
In FIG. 1, the second extractive distillation unit 30 further performs extractive distillation (second extractive distillation) on the fraction (G) containing high-purity isoprene to separate it into a fraction (A) and an extract (B). A second extractive distillation column 15 and a stripping column 16 for removing the solvent from the extract.

  In the second extractive distillation column 15, the solvent is supplied to the upper stage (upper side in the vertical direction) from the supply stage of the fraction (G) containing high-purity isoprene distilled from the fractional distillation tower 21, and the distillation containing high-purity isoprene is contained. The fraction (G) is further subjected to extractive distillation (second extractive distillation), thereby distilling the fraction (A) containing higher-purity isoprene from the top of the column and being more soluble in the solvent than isoprene. The extract (B) containing (for example, cyclopentadiene or the like) is taken out from the bottom of the column. In the stripping tower 16, the solvent is removed from the bottom of the tower, and a substance that is more soluble than isoprene is distilled from the top of the tower. In addition, the solvent collect | recovered by the stripping tower 16 can be reused arbitrarily in the 1st extractive distillation tower 12, the 2nd extractive distillation tower 15, etc.

  In addition, as a solvent supplied to the second extractive distillation column 15, for example, a known solvent used for extractive distillation of a C5 fraction such as a solvent described in International Publication No. 99/051552 is used. it can. Among these, amide compounds are preferable, and dimethylformamide is more preferable. By using an amide compound, particularly dimethylformamide, as the extraction solvent, other extractive distillation can be efficiently performed.

<Removal process>
In the method for separating and recovering isoprene of the present invention, the polymerization inhibitor used in the fractional distillation in the fractional distillation column 21 is removed from the fraction containing the high-purity isoprene. Thus, by removing the polymerization inhibitor used in the fractional distillation in the fractional distillation tower 21 from the fraction containing the high-purity isoprene, it is possible to prevent the polymerization inhibitor from being contained in the high-purity isoprene. it can. Specifically, when a polymerization inhibitor is contained in high-purity isoprene, polymerization is hindered even if it is attempted to polymerize high-purity isoprene. However, if the polymerization inhibitor used in the fractional distillation in the fractional distillation column 21 is removed from the fraction containing the high-purity isoprene, the polymerization is prevented from being inhibited when the high-purity isoprene is polymerized. be able to.
There is no restriction | limiting in particular as a removal method of a polymerization inhibitor, For example, the method of wash | cleaning the fraction containing a high purity isoprene using water, the method of isolate | separating by distillation, etc. can be used.

(Isoprene separation and recovery equipment)
The isoprene separation and recovery apparatus of the present invention can be suitably used when separating and recovering isoprene using the above-described isoprene separation and recovery method. An example of the isoprene separation and recovery apparatus of the present invention has a configuration as shown in FIG.

  Here, the separation and recovery apparatus 100 shown in FIG. 1 extracts and distills the mixed fluid as a raw material to obtain a fraction (X) containing crude isoprene, and the fraction obtained by the extractive distillation unit 10. (X) was fractionally distilled to enrich a fraction (E) containing impurities having a lower boiling point than isoprene, a fraction (F) containing impurities having a higher boiling point than isoprene, and a high-purity isoprene. A fractional distillation section 20 for obtaining high-purity isoprene as a fraction (G), and a fraction (G) enriched with isoprene are further subjected to extractive distillation to obtain a fraction containing higher-purity isoprene. And a two-extraction distillation unit 30. In the separation / recovery device 100, the mixed fluid can be a C5 fraction produced as a by-product when ethylene is produced by steam cracking of hydrocarbons or other high-temperature treatment.

<Extraction distillation section>
In FIG. 1, the extractive distillation unit 10 has a supply port for supplying a mixed fluid raw material containing isoprene such as a C5 fraction, and extractive distillation of the mixed fluid raw material supplied through the supply port ( And a first extractive distillation column 12 for separating into a fraction (C) and an extract (D).

  In the first extractive distillation column 12, the solvent is supplied to the upper stage (upper vertical direction) from the supply stage of the mixed fluid, and the mixed fluid is subjected to extractive distillation (first extractive distillation). A distillate (C) containing very insoluble pentane, pentene, etc. is distilled from the top of the column, and an extract (D) containing isoprene, 1,4-pentadiene, 2-butyne, piperylene, cyclopentadiene, etc. Remove from the bottom.

  As the solvent supplied to the first extractive distillation column 12, a known solvent used for extractive distillation of the C5 fraction such as the solvent described in International Publication No. 99/051552 is used. it can. Among these, amide compounds are preferable, and dimethylformamide is more preferable. By using an amide compound, particularly dimethylformamide, as the extraction solvent, extractive distillation can be performed efficiently.

  In the stripping tower 13, the solvent is taken out from the bottom of the tower, and the fraction (X) containing isoprene, 1,4-pentadiene, 2-butyne, piperylene, cyclopentadiene, etc. (including crude isoprene) from the top of the tower. Distillate). In addition, the solvent collect | recovered by the stripping tower 13 can be reused by the 1st extractive distillation tower 12, the 2nd extractive distillation tower 15, etc. arbitrarily.

<Division distillation part>
In FIG. 1, the fractional distillation unit 20 has a supply port for supplying, for example, a fraction (X) (a fraction containing crude isoprene) obtained by removing the solvent from the extract (D), A fractional distillation column 21 is provided for fractional distillation (division distillation) of the fraction (X) supplied via the supply port.
For example, the fractional distillation column 21 distills a fraction (E) containing low-boiling impurities such as 1,4-pentadiene and 2-butyne from the top of the tower, and a fraction containing high-boiling impurities such as piperylene ( F) is removed from the bottom of the column, and a fraction (G) containing high-purity isoprene is distilled from the central region of the column.

<Second extractive distillation section>
In FIG. 1, the second extractive distillation unit 30 further performs extractive distillation (second extractive distillation) of a fraction (G) containing high-purity isoprene to obtain a fraction (A) ( Furthermore, a second extractive distillation column 15 that separates into a fraction containing a high-purity isoprene and an extract (B) and a stripping column 16 that removes the solvent from the extract are provided.

  In the second extractive distillation column 15, the solvent is supplied to the upper stage (upper side in the vertical direction) from the supply stage of the fraction (G) containing high-purity isoprene distilled from the fractional distillation tower 21, and the distillation containing high-purity isoprene is contained. The fraction (G) is further subjected to extractive distillation (second extractive distillation), thereby distilling the fraction (A) containing higher-purity isoprene from the top of the column and being more soluble in the solvent than isoprene. The extract (B) containing (for example, cyclopentadiene or the like) is taken out from the bottom of the column. In the stripping tower 16, the solvent is removed from the bottom of the tower, and a substance that is more soluble than isoprene is distilled from the top of the tower. In addition, the solvent collect | recovered by the stripping tower 16 can be reused arbitrarily in the 1st extractive distillation tower 12, the 2nd extractive distillation tower 15, etc.

  In addition, as a solvent supplied to the second extractive distillation column 15, for example, a known solvent used for extractive distillation of a C5 fraction such as a solvent described in International Publication No. 99/051552 is used. it can. Among these, amide compounds are preferable, and dimethylformamide is more preferable. By using an amide compound, particularly dimethylformamide, as the extraction solvent, other extractive distillation can be efficiently performed.

  The isoprene separation and recovery apparatus of the present invention has been described above using an example, but the isoprene separation and recovery apparatus of the present invention is not limited to the above example. Moreover, the structure of the extractive distillation part 10, the fractional distillation part 20, and the other extractive distillation part 30 is not limited to the said structure, It can change into the arbitrary structures which can isolate | separate and collect isoprene.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited to these Examples.

(Example 1)
Isoprene was separated and recovered using the separation and recovery apparatus 100 shown in FIG. Specifically, isoprene was separated and recovered from a mixed fluid consisting of a C5 fraction produced as a by-product when ethylene was produced by steam cracking of hydrocarbons or other high-temperature treatment. The amount of isoprene in the mixed fluid consisting of the C5 fraction was 20% by mass.
Moreover, the composition of the mixed fluid (C5 fraction), fraction (C), fraction (E), fraction (F), fraction (G) was measured using a gas chromatograph (manufactured by Agilent Technologies, 7890A). Measurement was performed under the following conditions. The results are shown in Table 1.
Gas chromatograph: Agilent (registered trademark) 7890A (manufactured by Agilent)
Column: Agilent 19091P-S33, 30.0 m × 250 μm × 5.00 μm
-Column temperature: 35 ° C x 2.5 minutes-> Temperature rise at 5 ° C / min-> 100 ° C-> Temperature rise at 10 ° C / min-> 180 ° C x 10 minutes-Injection temperature: 200 ° C
-Detector temperature: 200 ° C
Carrier gas: Helium Split ratio: 200/1
・ Detector: FID

(Comparative Example 1)
In Example 1, isoprene was separated and collected in the same manner as in Example 1 except that the separation and recovery apparatus 200 shown in FIG. 2 was used instead of using the separation and recovery apparatus 100 shown in FIG.
The separation and recovery apparatus 200 is the same except that the fractional distillation unit 20 in FIG. 1 is replaced with an impurity removal unit 40.

<Impurity removal section>
The impurity removal unit 40 includes a low boiling point removal tower 41 for removing impurities having a lower boiling point than isoprene, and a high boiling point removal for removing impurities having a higher boiling point than isoprene, which are contained in the fraction (X). And a tower 42.

  In the low boiler removal column 41, the fraction (E) containing impurities having a boiling point lower than that of isoprene is distilled from the top of the tower, and the bottoms enriched in isoprene are taken out from the bottom of the tower.

  In the high boiler removal tower 42, the fraction (G) further enriched in isoprene is distilled from the top of the tower, and the fraction (F) containing impurities having a higher boiling point than isoprene is removed from the bottom of the can. Let it come out.

  In Example 1 and Comparative Example 1, when the operation was stopped after one year of continuous operation and the inside of the distillation column was visually confirmed, Example 1 produced less isoprene polymer than Comparative Example 1.

  According to the method and apparatus for separating and recovering isoprene of the present invention, by performing fractional distillation, it is possible to reduce the heat load and reduce the amount of isoprene polymer produced. It is possible to reduce the frequency of polymer cleaning that needs to be performed with the operation stopped.

DESCRIPTION OF SYMBOLS 10 Extractive distillation part 12 1st extractive distillation tower 13 Stripping tower 15 Second extractive distillation tower 16 Stripping tower 20 Division distillation part 21 Division distillation tower 30 Second extraction distillation part 40 Impurity removal part 41 Low boiling point removal tower 42 High boiling point substance Removal tower 100 Separation and recovery device 200 Separation and recovery device

Claims (13)

A method for separating and recovering isoprene from a mixed fluid containing isoprene, comprising:
Extractive distillation step of extracting the mixed fluid to obtain a fraction containing impurities having a lower solubility in the extraction solvent used in the extractive distillation than isoprene and a fraction containing crude isoprene;
The fraction containing the crude isoprene is fractionally distilled to obtain a fraction containing impurities having a boiling point higher than that of isoprene, a fraction containing impurities having a boiling point lower than that of isoprene, and a fraction containing isoprene having a high purity. A fractional distillation process;
A method for separating and recovering isoprene.   The method for separating and recovering isoprene according to claim 1, wherein the extraction solvent in the extractive distillation step is an amide compound.   The method for separating and recovering isoprene according to claim 2, wherein the amide compound is dimethylformamide.   The fraction containing the high-purity isoprene is further subjected to extractive distillation, and a fraction containing impurities having higher solubility in the extraction solvent used in the extractive distillation than isoprene and a fraction containing higher-purity isoprene are obtained. The method for separating and recovering isoprene according to any one of claims 1 to 3, further comprising a second extractive distillation step to be obtained.   The method for separating and recovering isoprene according to claim 4, wherein the extraction solvent in the second extractive distillation step is an amide compound.   The method for separating and recovering isoprene according to claim 5, wherein the amide compound is dimethylformamide.   The method for separating and recovering isoprene according to any one of claims 1 to 6, wherein the isoprene concentration of the fraction containing impurities having a boiling point lower than that of isoprene is 5 mass% or more and 90 mass% or less.   The method for separating and recovering isoprene according to any one of claims 1 to 7, wherein in the fractional distillation step, fractional distillation is performed in the presence of a polymerization inhibitor of 1 to 100 mass ppm with respect to the crude isoprene. Performing fractional distillation in the fractional distillation step in a fractional distillation column,
The method for separating and recovering isoprene according to any one of claims 1 to 8, wherein a polymerization inhibitor is supplied from an upper part in the vertical direction of the fractional distillation column.   The method for separating and recovering isoprene according to any one of claims 1 to 9, wherein the fraction containing the high-purity isoprene is a gas.   The method for separating and recovering isoprene according to any one of claims 1 to 9, further comprising a step of removing a polymerization inhibitor from the fraction containing the high-purity isoprene. A feed port for supplying a mixed fluid containing isoprene, extract-distilling the mixed fluid, a fraction containing impurities having lower solubility in the extraction solvent used in the extractive distillation, and crude isoprene An extractive distillation section to obtain a fraction containing
A supply port for supplying the fraction containing the crude isoprene; fractional distillation of the fraction containing the crude isoprene; and a fraction containing impurities having a boiling point higher than that of isoprene; and a lower boiling point than that of isoprene. An isoprene separation and recovery device comprising: a fractional distillation unit that obtains a fraction containing impurities and a fraction containing high-purity isoprene.   A supply port for supplying the fraction containing the high-purity isoprene; the fraction containing the high-purity isoprene is further subjected to extractive distillation; and the solubility in the extraction solvent used for the extractive distillation is higher than that of isoprene. The apparatus for separating and recovering isoprene according to claim 12, further comprising a second extractive distillation section for obtaining a fraction containing higher impurities and a fraction containing higher-purity isoprene.

Images