JPS60184030A - Recovery of 1,3-butadiene - Google Patents

Abstract

PURPOSE:To recover the titled compound from the distillate of 4C hydrocarbons, effectively, by a two-stage extractive distillation process, by extracting the 5C component in the 4C hydrocarbon fraction as the side stream from the second extractive distillation column near the stage to feed the selective solvent, and discharging the component from the system through a heave- fraction separation column. CONSTITUTION:The butane-butnen fractions and 4C acetylene compounds are removed successively from the 4C hydrocarbon fraction 1 containing the titled compound admixed with a small amount of 5C hydrocarbon, by the two-stage extractive distillation process comprising the first extractive distillation step 2, the second extractive distillation step 10, and the solvent dissipation step 7, using the selective solvent 3, 9. Furthermore, the small amount of the impurities existing in the product are removed by the heavy-fraction separation column 24 and if necessary, the light-fraction separation column 27 to separate and recover the objective compound 29 in high purity. In the above process, the fraction rich in the 5C component is extracted as the side stream from the second extractive distillation column at the stage 18 near the stage 9 to feed the selective solvent, and discharged 26 from the system through the heavy-fraction separation column 24 after removing the selective solvent 20 from the stream. The accumulation of the 5C component in the second extractive distillation system 10 can be suppressed, and the objective compound can be recovered economically.

Description

Detailed Description of the Invention (Field of Application of the Invention) The present invention relates to a method for recovering 1,3-butadiene, and more specifically to a method for recovering 1,3-butadiene from a small amount of C% hydrocarbon obtained by a method such as naphtha cranking or dehydrogenation reaction. 1,3-
The present invention relates to a method for recovering 1,3-butadiene from a C4 hydrocarbon fraction containing butadiene.

(Background of the Invention) Extractive distillation is widely known as a method for separating and recovering high-purity butadiene in high yield from a C4 hydrocarbon fraction containing 1.3-butadiene (hereinafter abbreviated as butadiene). It is also practiced industrially. As the selective solvent in this case, for example, a polar substance such as acetonitrile, dimethylformamide, N-methylpyrrolidone, furfural, acetone, dimethylacetamide, or a mixture of these and water is used.

The raw C4 hydrocarbon fraction usually contains a small amount of 04 acetylenes, and a two-stage extractive distillation method is widely used to remove these C4 aceticines.

For example, Chem, Tech, 28 nog, Heft
8. Aug, 1976, pages 463-466 and Organic Synthetic Chemistry, Vol. 38, No. 6, pages 92-99, disclose a two-stage extractive distillation process for butadiene using dimethylformamide as a selective solvent.

In addition, Hydrocarbon Processing
Vol, 47. No. 11, pages 135-138 have N.
A two-stage extractive distillation method using -methylpyrrolidone as a selective solvent is disclosed, and Japanese Patent Application Laid-Open No. 47-34207 discloses a two-stage extractive distillation method using acetonitrile as a selective solvent.

In these methods, components with weak affinity for solvents (butane-butenes, etc.) are removed from butadiene as light fractions in the first extractive distillation step, and components with weak affinity for solvents are removed from butadiene in the second extractive distillation step. Components with a strong content (C4 acetylenes, etc.) are removed as heavy components, and the crude butadiene containing a small amount of impurities obtained in this way is purified in the next light fraction separation tower and/or heavy fraction separation tower to become a high-quality product. Purity of butadiene is obtained.

That is, in the conventional two-stage extractive distillation method, a raw hydrocarbon fraction is first supplied to a first extractive distillation column for removing butane-butenes, and the presence of a selective solvent supplied from near the top of the column is At the bottom, extractive distillation is performed to distill a butane-butene fraction from the top of the column. On the other hand, the selective solvent containing hydrocarbon components rich in butadiene recovered from the bottom of the first extractive distillation column is removed via the pre-solvent stripping column or directly.
The selective solvent supplied from near the top of the second extractive distillation column is supplied to a second extractive distillation process consisting of a second extractive distillation column and a solvent stripping column for removing harmful impurities such as 4-acetylenes. Extractive distillation is performed in the presence of the 04 acetylenes, and a crude butadiene fraction from which harmful components such as 04 acetylenes have been removed is recovered from the top of the second extractive distillation column. Next, a small amount of light components and/or heavy components mixed in this crude butadiene fraction are removed in a light fraction separation column and/or a heavy fraction separation column as described above, and high purity butadiene is separated and recovered. .

The raw C4 hydrocarbon fraction fed to these processes typically contains small amounts of 03 and C5 hydrocarbon components industrially.

Of these, most of the C3 hydrocarbon components are removed together with the butenes in the first extractive distillation step in the two-stage extractive distillation method, and the remaining portion (mainly composed of arene and/or methylacetylene A) is It is removed in a light fraction separation column after the second extractive distillation step.

On the other hand, regarding C5 hydrocarbon components, certain types of these, such as 05-05 rough ins and C5 mono-olefins, have relatively low boiling points (components with relatively low boiling points (for example, 05-05 hydrocarbons such as isopenkune and n-pentane). Paraffins and 3-methyl-1-[tetene 05 monoolefins), etc., tend to accumulate in the extractive distillation process when they are supplied to the extractive distillation process together with the raw material C4 carbon hydrogen. In order to forcefully discharge the gas from the system, excess energy is used in the conventional method described above.

Even if these C components accumulate in the extractive distillation column, they do not reach the point where operation becomes impossible, and are discharged out of the system little by little from the top and/or bottom of the column. (not concentrated). However, this accumulation of C5 components has an adverse effect on the separation of C4 acetylenes and other light harmful impurities, which is the objective of the second extractive distillation column.

Therefore, in the conventional method, extra energy is required to remove harmful impurities such as C4 acetylenes to a predetermined concentration or less, and an improvement has been desired.

As a method for avoiding the accumulation of C5 paraffins and light C5 monoolefins in the extractive distillation system, there is a method described in JP-A-53
According to this method, C- and hydrocarbons present in the fat solvent discharged from the extractive distillation zone for separating butane-butenes are removed from the strifping zone and Since it is concentrated in the vapor stream recovered from the flashing zone, a portion of the vapor stream is separated to remove the selective solvent and then fed to the separation zone (0g removal column) before the extractive distillation zone. In addition to removing the C5 component, butadiene contained in the branched stream is recovered.

Although this method is a preferable method for preventing the accumulation of C5 components in the extractive distillation system and for efficiently separating and purifying butadiene, it has the following serious drawbacks. That is, since the vapor stream recovered from the stripping zone and the flushing zone contains butadiene, C4 acetylene, etc. in addition to the concentrated CS component, butadiene in the branched vapor stream is recovered. In order to
c! In addition to the H component, it is necessary to separate 04 acetylenes, and for example, as shown in the same publication, it is necessary to separate the 04 acetylenes into a separation zone (C-di removal column) provided before the extractive distillation zone. is necessary. Therefore, in this method, regardless of the concentration of C5 components in the raw C4 hydrocarbon fraction, it is not only necessary to install a separation zone (c!i removal tower), but also to extract This increases the throughput in the distillation system, leading to an increase in throughput.

(Object of the invention) The object of the present invention is to eliminate the drawbacks of these conventional techniques and to
The accumulation of 05 components in the extractive distillation system is suppressed, and harmful substances such as C4 acetylenes are removed using a two-stage extractive distillation method from the C4 hydrocarbon fraction containing butadiene mixed with a small amount of C and hydrocarbons. 1.3-
The object of the present invention is to provide a method for recovering butadiene.

(Summary of the Invention) In order to achieve this objective, the present inventors conducted intensive research and found that Cs paraffins and light Cs monoolefins were added to the second extractive distillation column for removing C4 acetylene etc. from butadiene. It was discovered that there is a concentration expansion near the stage that supplies the selective solvent, and in this vicinity, the concentration of harmful components such as C4 acetylene is equal to the concentration in the crude butadiene obtained from the top fraction of the column. Almost no change (above the selective solvent feed stage, the 0 in crude butadiene
It was found that the concentration of 4 acetylenes hardly decreased. As a result of further studies based on these findings, we found that
A small amount of the vapor stream containing relatively high concentrations of the components is withdrawn as a side stream, and after removing the selective solvent contained in the side stream, it is transferred to the heavy fraction from butadiene provided downstream of the extractive distillation column. It has been found that the above-mentioned drawbacks of the prior art can be overcome by supplying the C5 component to a heavy fraction separation column for removing C5 and removing the C5 component contained in the side stream from the bottom of the column. Heading, we arrived at the present invention.

The present invention contains 1,3-butadiene as a main component and C
A first extractive distillation step for the purpose of separating butane-butenes using a selective solvent, using a raw hydrocarbon fraction containing C4 hydrocarbons and small amounts of Cs paraffins, light C, monoolefins, etc., and C4 acetylenes. A two-stage extractive distillation method consisting of a second extractive distillation step and a solvent dispersion step is used to separate and purify the crude 1,3-butadiene fraction. In a method for separating and recovering high-purity 1,3-butadiene by removing it in a heavy fraction separation column and/or a heavy fraction separation column according to the After extracting the fraction rich in 0.3 components as a side stream and removing the selective solvent contained in the side stream, this is supplied to a heavy fraction separation column and the C and components are discharged from the system. Characterized by urging.

The C4 hydrocarbon feedstock used in the present invention contains a small amount of 05 component obtained by naphtha cracking, dehydrogenation of a butane-butene fraction, etc., and generally also contains a small amount of 03 component. . The content of these components is
Although it varies depending on the design and operating conditions of the process such as naphtha cracking and dehydrogenation, the C5 component is generally 0.02~
The concentration is about 0.5% by weight. C4 supplied
If the concentration of C and hydrocarbon components in the hydrocarbon raw material is high, a depentanizer is installed before supplying it to the first extractive distillation column, and after removing most of the C5 components, it is fed to the first extractive distillation column. It is preferable to supply the C5 hydrocarbon component at a concentration of 0.
．． If the amount is 5% by weight or less, the 04 hydrocarbon raw material can be directly supplied to the first extractive distillation column.

In the method of the present invention, among the components, C5 paraffins (n-pentane, isopentane) and light C are mixed in a small amount in the C4 hydrocarbon raw material.

Monoolefins (such as 3-methylpentene) are fed as a side stream from a stage near the selective solvent supply stage of the second extractive distillation column, while heavy C, monoolefins (such as 2-methyl-2-butene) and C, Diolefins and C5 acetylenes are the second
C4 as a drifting stream from the middle stage of the solvent stripping tower during the extractive distillation process
It can be discharged out of the system together with acetylenes, etc., and efficient operating conditions can be maintained.

In the present invention, the position from which the fraction relatively rich in C5 components is extracted as a side stream of the second extractive distillation column is important. 2
In the second extractive distillation column for removing 04 acetylene from butadiene in the stage extractive distillation method, the selective solvent concentration in the liquid phase is lower above the selective solvent supply stage, so these C5 components are removed from butadiene. C4 as the main component
Although the relative volatility is lower than that of hydrocarbons, the concentration of the selective solvent in the liquid phase increases below the supply stage of the selective solvent. It has a higher relative volatility than butadiene, which occupies a fraction of The testes, these C, components have difficulty moving both above and below the extractive distillation column, and eventually tend to concentrate near the selective solvent feed stage. Therefore, in the present invention, it is preferable to extract a fraction rich in C-5 components from a stage near the selective solvent supply stage as a side stream. If the side stream is withdrawn too high, the concentration of the C5 component in the side stream will be low and the flow rate of the side stream will need to be increased to compensate for this, resulting in the selective solvent being removed from the side stream. This is not preferable because the amount of processing required in the removal step increases. On the other hand, if the side flow extraction position is too low, the 04
When the concentration of harmful substances such as acetylene increases and it is fed to a heavy material separation column, the column cannot remove these harmful substances, and as a result, high purity butadiene cannot be obtained. Based on the position of the supply stage -
It is preferable to extract the side stream from the position of Iθ~+5th stage.

The side stream withdrawn from a stage near the selective solvent supply stage may be drawn from the liquid phase or the gas phase if the position of withdrawal is above the selective solvent supply stage; In some cases, it is preferable to extract from the vapor phase. At this time, it is of course possible to extract from the liquid phase, but in this case, since the concentration of the selective solvent in the liquid phase is significantly higher than that in the vapor phase, it is necessary to increase the amount extracted, and from the side stream. The burden of the process of removing the selective solvent increases.

The amount of side stream withdrawn from the stage near the selective solvent supply stage of the second extractive distillation column depends on the concentration of the C5 component in the C4 hydrocarbon feedstock fed to the first extractive distillation column, but the amount of energization is extremely small. It is often less than 5% by weight (hydrocarbon basis - solvent free) of the C4 hydrocarbon feedstock feed, preferably less than 1% by weight. In addition, the amount of side stream to be extracted is determined from the viewpoint of suppressing the accumulation of C5 components and removing solvent as described below.
The concentration of the five components is preferably set to be 0.5 to 10% by weight, more preferably 1 to 5% by weight on a hydrocarbon basis.

Preferred methods for removing the selective solvent contained in the side stream extracted from the stage adjacent to the selective solvent supply stage include, for example, a distillation method, a water washing method, and the like. In the case of the distillation method, the side stream removed as a vapor stream is fed to the bottom of a separate solvent removal column, and the recovered solvent is obtained from the bottom of the cough column, which contains hydrocarbon components. Since the side stream is contained in the second extractive distillation column, it is returned to a stage adjacent to the stage from which the side stream was withdrawn (preferably the same stage). On the other hand, since a hydrocarbon fraction containing no solvent is obtained from the top of the solvent removal column, a portion is returned to the top of the solvent removal column as reflux, and the remainder remains in the vapor phase or is condensed into liquid. It is fed in phase form to the next heavy fraction separation column. In this case, an independent condenser may be provided at the top of the solvent removal column; It is also possible to feed the column overhead vapor stream directly to the center of the heavy fraction separation column, and to withdraw a liquid stream from a stage adjacent to the feed stage of the vapor stream and feed it as reflux to the top of the solvent removal column. . The latter method is more preferable in terms of improving the economic efficiency of the process.

If the side stream fed to the solvent removal column is withdrawn in liquid phase from the second extractive distillation column, a reboiler is usually provided at the bottom of the solvent removal column.

On the other hand, in the case of the water washing method, which is another preferred method for selective solvent removal, the side stream fed to the water washing tower may be a vapor stream or a liquid stream (
(the liquid extracted from the second extractive distillation column as a liquid stream or the vapor stream condensed in a condenser)
This stream may be fed to the bottom of the washing column, while water substantially free of selective solvent is fed from the top of the washing column. A selective solvent-free hydrocarbon stream is obtained from the top of the water washing column, and this stream is fed to the central part of the heavy fraction separation column. On the other hand, a mixture of selective solvent and water is obtained from the bottom of the water washing column, and this stream is concentrated in a separately provided solvent concentration column and then returned to the extractive distillation system.

The side stream drawn off from the second extractive distillation column is fed to the heavy fraction separation column after removing the selective solvent in this way. The side stream is fed to the heavy fraction separation column at the stage to which the crude butadiene stream from the second through-hole extractive distillation column is fed, or at a stage near the bottom thereof.

At this time, if it is supplied too downwardly, it will lead to loss of butadiene, which is undesirable. It is also possible to feed the crude butadiene to a stage above the crude butadiene supply stage, but if it is fed too high, the C5 component will be mixed into the butadiene product.

Butadiene obtained as the top fraction of the heavy fraction separation column may still contain harmful impurities such as methylacetylene and allene, depending on the type of C4 hydrocarbon raw material used. In that case, the top fraction of the heavy fraction separation column is further supplied to the heavy fraction separation column to remove these harmful impurities, thereby producing a highly pure bottom fraction of the heavy fraction separation column. Butadiene is obtained. In the case of the present invention, butadiene is purified first in a heavy fraction separation column and then in a heavy fraction separation column, as has been conventionally done. Methylacetylene may be included, which is undesirable because it will be mixed into the butadiene product.

(Embodiments of the Invention) The present invention will be explained in more detail below with reference to the drawings. For the sake of clarity, most of the pumps, heat exchangers, etc. that are not particularly necessary for the explanation are omitted from the diagram, and only the main parts are shown.

FIG. 1 is an apparatus system diagram showing one embodiment of the method of the present invention. In the figure, first, a C4 hydrocarbon feedstock containing butadiene mixed with a small amount of C5 component is supplied to the middle stage of a first extractive distillation column 2 through a conduit 1.

A selective solvent is supplied to the top of the first extractive distillation column 2 via a conduit 3. A butane-butene fraction is discharged from the top of the first extractive distillation column to the outside of the system via conduit 4, while a butane-butene fraction is discharged from the bottom of the column as a hydrocarbon component enriched with butadiene and containing C4 acetylenes, C5 components, etc. The solvent is discharged via line 5 and, after combining with the bottom fraction of the second extractive distillation column 10 which is discharged via line 12, is fed via line 6 to the top of the solvent stripping column 7. A vapor stream from the top of the solvent stripping column 7 is supplied to the bottom of the second extractive distillation column 10 via a conduit 8, while a selective solvent and C4 are supplied near the top of the second extractive distillation column 10. By ensuring the necessary stages for the separation of hydrocarbons,
A selective solvent is supplied by conduit 9. A side stream is withdrawn as a vapor stream from a stage adjacent to the selective solvent supply stage of the second extractive distillation column 10 through a conduit 18, condensed in a condenser 19, and then supplied to the bottom of a water washing column 20. From the top of the water washing column 20, washing water is supplied via conduit 21, and from the top a stream of hydrocarbons substantially free of selective solvent and relatively enriched in C% acid components is fed via conduit 22. can get.

This stream is fed to the middle stage of the heavy fraction separation column 24 via conduit 22a or 22b. On the other hand, a selective solvent diluted with water is obtained from the bottom of the water washing column 20 via a conduit 23, which is concentrated in a solvent recovery device (not shown) and then returned to the extractive distillation system.

A vapor stream is extracted from the top of the second extractive distillation column 10 via a conduit 11, and is supplied directly to the middle stage of the heavy material separation column 24 without being condensed. On the other hand, the heavy material separation tower 24
The liquid is withdrawn as a side stream from the middle stage (the stage from which it is withdrawn is preferably the same as the supply stage of conduit 11 or a stage near it) and is supplied as reflux to the top of the second extractive distillation column 10 via conduit 30. be done.

A side stream is extracted as a vapor stream from the middle stage of the solvent stripping column 7 via a conduit 14 and supplied to the bottom of a solvent recovery column 15, while a liquid stream is drawn from the bottom of the solvent recovery column via a conduit 17. It is extracted and returned to the solvent stripping tower 7. The feed stage side stream to the solvent stripping column 7 in conduit 17 is in a stage adjacent to, preferably the same stage as, the stage from which it is withdrawn by conduit 14.

From the top of the solvent recovery column 15, a C4 acetylene-enriched fraction from which the selective solvent has been substantially removed is obtained, and is passed through the conduit 1.
6 and is discharged from the system. A substantially hydrocarbon-free stream is obtained from the bottom of the solvent stripping column 7 via conduit 13, and this stream is cooled to a predetermined temperature by a heat recovery step and a cooler (none of which are shown). After that, a portion is recycled to the first extractive distillation column 2 via conduit 13, and the remainder is recycled to the second extractive distillation column 10 via conduit 9.

From the bottom of the heavy fraction separation column 24, heavy olefins (trans and cis-butene-2), 1
．． 2-butadiene, the C5 component, etc. are extracted through the conduit 26 and discharged outside the system. On the other hand, from the top of the heavy fraction separation column 24, butadiene mixed with a small amount of methylacetylene, allene, etc. is fed through a conduit 25, and this flow is supplied to the heavy fraction separation column 27. Heavy components such as methyl acetylene are removed from the top of the heavy fraction separation column 27 and passed through the conduit 2.
8 is discharged to the outside of the thread, and high-purity butadiene is thus obtained from the bottom of the heavy fraction separation column via conduit 29.

The configurations of the first extractive distillation step and the second extractive distillation step shown in FIG. 1 are merely examples, and it is obvious that the present invention can be applied to various conventionally known configurations. .

Next, the present invention will be explained in more detail with reference to comparative examples and examples.

Comparative Example In FIG. 1, butadiene was purified by the conventional method using an acetonitrile/water (90/10 weight ratio) mixture as the selective solvent and without using the equipment and lines 18 to 23.

The operating conditions of the heavy fraction separation column 24 were as follows.

Total number of stages 100 Raw material supply stage (from bottom) 45 Tower top pressure (kg'/c G) 3.5 Tower top degree ('
C) 41 Reflux Ratio 5.0 The flow rate and composition of the hydrocarbon components in the main conduits after the refining process are shown in Table 1. Note that in Table 1, there is a stream containing a selective solvent (eg, conduit 4), but for the sake of clarity only the values after removing the selective solvent are shown.

FIG. 2 also shows the second extractive distillation column 10 and the solvent stripping column 7.
It shows the composition distribution of the C5 component inside. From Figure 2, C, the components are the second extracted vapor 1. [1310] The force of concentration near the supply stage of the selective solvent (as can be clearly seen. In Fig. 2, A is for the comparative example, B6 is for the example, C is the bottom of the solvent stripping column 7, At the extraction stage of the conduit 14 of the D&M container stripping tower 7, several tower tops (=first
The bottom of the extractive distillation column 10 QIX), F is the second extractive distillation column 1
0, the feed stage of conduit 9 (= withdrawal stage of conduit 18), G designates the column top of second extractive distillation 1, moss 10, respectively.

Table 1 in the margin below Using an acetonitrile/water (90/10 weight ratio) mixture as the selective solvent, following the steps in the system diagram shown in Figure 1, raw materials with the same composition as the comparative example (conduits in Tables 1 and 2) (described in column 1) was used to purify butadiene.

A vapor stream of 538.5 kg/H (505.3 kg/H as a hydrocarbon component) is extracted from the same stage as the selective solvent supply stage of the second extractive distillation column 10 through the conduit 18, and is transferred to the condenser 1.
After being condensed in step 9, it was supplied to the bottom of a water washing tower 20.

The water washing tower 20 is made of porcelain packing (Intalox 5addl
A packed tower filled with e) to a height of 9 m, and water flows from the top of the tower to 6 m.
It was supplied via conduit 21 at a flow rate of 00 kg/H. A hydrocarbon fraction 505, 3 kg/H, substantially free of acetonitrile, was obtained from conduit 22, and this stream was fed to the 40th stage from the bottom of heavy fraction separation column 24 via conduit 22b.

The flow rate and composition of the hydrocarbon components in the main conduits after the refining process are shown in Table 2.

Table 2 Table 2 (Continued) In addition, FIG. 2 shows the composition distribution of the 05 component in the second extractive distillation column 10 and the solvent stripping column 7.

0 near the selective solvent supply stage compared to the distribution in the comparative example.
It can be seen that the concentrations of the five components have decreased significantly.

According to an embodiment of the invention, 05 in the second extractive distillation column 10
By suppressing the accumulation of components, the separation efficiency of butadiene and 04 acetylenes was improved, and the amount of reflux supplied through the conduit 30 could be significantly reduced compared to the case of the comparative example.

Furthermore, compared to the comparative example, the load fluctuations of the bottom reboiler of the solvent stripping tower 7 and the heavy fraction separation tower 24 were as follows.

Solvent stripping tower 7 Reboiler 555 X 10 J5Kca
l/H reduction heavy fraction separation column 24 Reboiler 50X10βK
cal/H increase total 505 x 10 J6Kcal/
The quality of the product butadiene obtained via HM conduit 29 was comparable to that of the comparative example.

(Effects of the Invention) As described above, according to the method of the present invention, 1 part of the C% acid component contained in a small amount in the raw material is extracted as a side stream of the second extractive distillation column 10 and supplied to the heavy fraction separation column 24. This treatment suppresses the accumulation of O8 components in the second extractive distillation system, so that harmful substances such as C4 acetylene can be effectively removed.

In addition, unlike conventional technology, there is no need to recycle the side stream extracted to suppress the accumulation of C5 components before the first extractive distillation column, and it can be treated in the heavy fraction separation column, reducing the increase in throughput. In addition, when the concentration of C and components in the C4 raw material hydrocarbon fraction is low, it is not necessary to provide an independent depentanizer.
In these respects, it is possible to achieve a process that is much more energy-saving than the conventional technology.

[Brief explanation of drawings]

FIG. 1 is an apparatus system diagram showing one example of the method of the present invention, and FIG. 2 shows the concentration distribution of the C5 component in the second extractive distillation column 10 and the stripping column 7 for the example of the present invention and the comparative example. FIG. 2... First extractive distillation column, 7... Solvent stripping column, 10.
...Second extractive distillation column, 15...Solvent recovery column, 20...
-Water washing tower, 24...heavy fraction separation tower, 27...heavy fraction separation tower. Agent Patent Attorney Takeshi Kawakita

Claims (1)

[Claims] (1) A feedstock hydrocarbon fraction containing C4 hydrocarbons containing 1,3-butadiene and a small amount of C, paraffins and light 0% monoolefins was used for the purpose of separating bukunuptenes using a selective solvent. First extractive distillation step, C
A small amount of impurities mixed in the crude 1,3-butadiene fraction obtained by separation and purification using a two-stage extractive distillation method consisting of a second extractive distillation step and a solvent diffusion step for the purpose of separating 4-acetylenes, In a method for separating and recovering high-purity 1,3-butadiene by removing it in a heavy fraction separation column and, if necessary, in a heavy fraction separation column, a relative C. A method characterized by extracting a fraction rich in components as a side stream, removing a selective solvent contained in the side stream, and then supplying this to a heavy fraction separation column to discharge C5 components out of the system.
, 3-butadiene recovery method.