JPS5879932A - Purification of butadiene or isoprene - Google Patents

Abstract

PURPOSE:In recovering the titled high-purity substance from a mixture of 4-5C hydrocarbons by two-step extractive distillation, to use quantity of heat effectively, by feeding a side flow taken out from a solvent stripper to a heat recovery process, returning it to a plate near to the plate from which the side flow is taken out. CONSTITUTION:A raw material hydrocarbon is fed from the pipe 1 to the first extractive distillation column EI, a selective solvent is fed from the pipe 3 to it to carry out extractive distillation, and a flow comprising diolefins, acetylenes, and the solvent is fed from the bottom of the column to the first solvent stripper column SI. The solvent is circulated from the bottom of the clumn to the first extractive distillation column EI, and a flow of hydrocarbon is sent from the top of the column to the second extractive distillation column EII. The desired substance is obtained from the pipe 10, a flow comprising the acetylenes and the solvent is sent from the bottom of the column to the second solvent stripper column SII, and the acetylenes are discharged from the pipe 13. A side flow is taken out from the pipe 14, subjected to heat exchange with a substance to be heated by the heat exchanger 15, and condensed and returned again to the stripper column SII.

Description

[Detailed description of the invention] or 2-methyl-1,robutadiene (abbreviated as
Regarding the purification method of isoprene (hereinafter abbreviated as isoprene), details 1-7 refer to the method for selectively purifying acetylenes having the same carbon number as butadiene or isoprene and /1 or allene from a solvent stripping column in the extractive distillation purification process using a polar solvent. The present invention relates to a method for efficiently refining butadiene 1 or isoprene by recovering the heat removal energy from discharging such substances.

Conventionally, C4t was obtained by dehydrogenation of naphtha by heating, etc., but extractive distillation or chilling is used as a method for recovering butadiene or isoprene from a C5 hydrocarbon mixture. Particularly in recent years, the removal of acetylenes has been developed. 3.Butadiene or isoprene is widely known as a known technology (hydrocarbon mixture of 144 or 05!). A relatively common understanding is that ``roughfins and olefins are discharged as a stream from the first extraction III steaming column and turned into solvents'': Butadiene, inoprene, and acetylene, which are easy to extract, are The hydrocarbon mixture '121 consisting of and allenes is taken out in the column J stream and E~ of the first extractive distillation column together with the selected P1 bath agent. 'When the WI component is used, acetylenes, arrays LJ outside (/(cyclo-S notadigon,
Diolefins such as heglylene, sulfur compounds such as dimenal sulfite 9 (J-!, 1.-Fbuse 11/
Allenes, allenes, etc. are separated and abbreviated as aarenes, etc.) are also taken out as a bottom stream.

2-stage extraction Uodome method 2 kinds of knowledge type +/(Separated. 1
The 1st and 2nd stage extraction boxes are independent 1~, and each extractive distillation process has an independent bath agent diffusion tower.The first extractive distillation tower is t, is supplied to the first solvent stripping tower, and the hydrocarbon mixture l, extraction solvent and VC part, l1i1t
This is a method in which the 1-meritized hydrogen mixture obtained from the top of the column is fed to the lower stage of the second distillation distillation. (1) Example f Hyd
rocarbon Processing Voco. 4
5//15. -1 The process using dimethinotoformamide as a selective bath agent is slightly different from I P 151 to 154.

With one additional branch (A and the second extractive distillation column or the common bath agent stripping column are aligned in Y-Irumo Q), the column r = flow of the first extractive distillation column is the first bath stripping column. This is a method in which the water is supplied to the iM Han No. 2 extractive distillation column without passing through the defeat column.

For example, HyarOCar'1) OII Pro
coinri, n)r Vo”, 47-bi 11P135~
Select N-methylpyrrolidone for 168.1. Anti-solvent and [7] processes are disclosed. .

°, generally ° is circled on the second extractive distillation shield 1.
[〈, allenes, etc., butane monomer or isozo 1/
N'nili bath salts, 41's 1q: Trade advantage Jl
l L'-c, /? , the activity of moon insect pollinators such as staghorn fecunds, etc. is significantly increased.
Butadiene and isoprene with a purity of 1.6, which is not saturated in water, is discharged to the second extractive distillation column as the old stream, while it is discharged to the acetylene column 1 as the Tsukudano J stream. The butadiene 4 or isoprene it 1' taken off as the column of stream of the second extractive distillation column is co-fed with 1 to the final fractional distillation]-1 °l'' to remove the impurity 1 of l i〒1; 1%
Frontal phytadiene and also 021-isoprene are produced.

As a method for removing acetylene, ``'1, etc. in the second extractive distillation step, Ind, Kn)<, C, 11em, V
A two-stage extractive distillation process using N-methylpyrrolidone as a dialysis 1'llI:# cut is disclosed in P43-48. According to this method, a solvent containing a-5=cetylenes, etc. is taken out from the middle stage of the bath agent stripping tower as a side vapor stream and is supplied to the solvent separation tower, and the two properties of the bath agent dissolving in water are removed. Use 1. Water is fed near the top of the solvent separation column, and the solvent is removed by +pJ IIX l- through a water shaft.

The solvent dissolved in water is withdrawn as the bottom stream of the solvent separation column and returned to the solvent extraction VliMb, while the hydrocarbon mixture containing acenalene etc. is discharged as the bottom stream of the solvent separation column. be done.

Ushida Special Publication No. Sho 47-2702 Stripping Tower (In this explanation, it corresponds to the second extractive distillation step) The bath agent is separated in the column and the acetylenes etc. of the mixture to be extracted and distilled are removed from the concentrated pods. 1j flow with equal concentration) 1
614 describes a method of removing aacerenes and the like by discharging the product from a Zving column, and then recovering butadiene or inoprene from a stripping column. In this example, a single stream containing acerenes, etc. is cooled through a ``Kojiji 6-han'' (7), and then sent to a separation tower or combined with raffinate to a single-rotating disk tower-type washing tower. There, water is supplied to a separation column or a resuscitation column 6-, and the solvent is removed by washing with water. I'm VL.

Furthermore, %Kai No. 54-138508? According to Haruka,
A method for removing acetylenes and the like from a solvent stripping tower is described in Section 8. In this method, hydrocarbons containing acetylenes, etc. are separated from ordinary substances in a tower (117), and the bath agent is circulated (also, in order to
6r, lt 140-1300.

The inventors examined the prior art described above from the standpoint of effective use of the 1-key, and it became clear that Ta.

That is, UC iris in the C4 or C5 fraction, l'1.
-(-kuru-notaji-cho-n-Also, d isoprene and the same--consisting of carbon streaks. The majority of the flow supplied to the solvent stripping tower, which separates the acetylenes, etc., is solvent.Considering these special requirements (7), we will conduct a detailed analysis of the separation of the acetylenes, etc. and bath agents in the solvent stripping tower. - As a result, it was found that the recovery section below the raw material supply stage is responsible for the flow rate required for separation in this column, and the concentration section above the raw material supply stage can meet the required flow rate even with a much lower reflux flow rate. Separation of acetylenes, etc. and solvents is possible
I discovered the surprising fact that EJ is Noh. In other words, in the conventional technology, much more reflux was applied in the concentration section of the solvent stripping column than the amount of reflux required for separation, and a large amount of heat was provided at the top of the column to generate the reflux. This means that the water was drained out of the system from the condenser, or the water supplied from the outside to the top of the tower changed the quality of the cedar, which is not Jigatsu 1, and was not used for any kind of ringing. .

Therefore, the present inventors have carefully considered ways to utilize the facts found as a result of detailed analysis of the tower to rationalize the process, and as a result, from the stage near the raw material supply stage of the solvent stripping tower,
After the side vapor stream is withdrawn and sent to a heat recovery step to condense the side vapor stream, the side vapor stream of the solvent release column is withdrawn and returned to the near-sui stage. The present invention has been achieved by discovering that the process can be made easier and more efficient without affecting the separation of the target R component in the first extractive distillation step or the second extractive distillation step. Ta.

That is, the present invention is directed to the presence of a selective solvent.
When high-purity butadiene or isosol is extracted once from a hydrocarbon mixture of C4t and C5 by the stage extractive distillation method, a small amount of it is contained in the bottom of the column taken out from the extractive distillation Wf column. Fusetylenes having the same number of carbon atoms as the broken zotanene or isoprene are separated from the solvent stripping tower and extracted as a vapor phase from a stage near the raw material supply stage of the stripping tower. Acetylene Rui Temple J
Kanzawa I11゛A heat recovery process of a single rectangular flow consisting of a solvent
After supplying the bulking agent, it is returned to stage F near the extraction stage of the side stream in H1 before the blowing agent stripping tower. This provides a method to do so.

The amount of side vapor stream withdrawn from the solvent stripping column according to the present invention is exclusive of that required by the concentration section of the column. The stage for withdrawing one side steam flow may be the one closest to the raw material supply stage, or preferably it is withdrawn from the raw material supply stage. On the other hand, the return stage for the condensate after heat recovery can be provided as long as it is a stage near the steam flow withdrawal stage [7, but it is preferable that it is the same stage as the side steam flow withdrawal stage. .

In the present invention, selective solvents that can be used include polar substances such as acetolyl N-methylpyrrolidine, dimethylacetamidofurfural, and acetone, or 0 to 2% of water added to them.
Such as an aqueous mixture containing 0% by weight.

A specific example is given of any place where the temperature of the side stream collected from the m-agent diffusion tower is 1°C higher than the temperature of the side stream collected from the m-agent diffusion tower and where the difference in temperature and temperature can be 5°C or more. ■ Glue boiler or Zydriwheeler (see Figure 4) at a stage near the bottom of the first extractive distillation column ■ Hydrocarbons rich in butarenin or isoprene supplied from the first extractive distillation step A side rewheeler (fifth
(See figure) 1 0- ■ Raw material preheater for the hydrocarbon mixture of C4 i kil: Cs that is the raw material ■ Pretreatment process before the extractive distillation process (preheater or boiler in '11) ■ The second extractive distillation column A preheater for the loading process to remove impurities from the crude butadiene or isoprene distilled out as the overhead stream7. Examples include "sun-dashi" and reboilers.

Among these, it is desirable to be able to minimize contamination due to leakage troubles in heat exchangers, etc., and to have a relative heat retention ratio of 111 to the thermal energy of the side force IMI <, 745 times 115! When carrying out the operation, 0 and (ri) are particularly preferable as they have little effect on the soil during operation.

This research will be explained below with reference to the drawings. For the sake of brevity, the figure omits most of the 71-sump, heat exchanger toilet, girder, etc. that are not necessary for the explanation, and only the main parts are shown.

Depending on the type of raw material, a pre-treatment step and/or a post-treatment step may be provided before or after the steps shown below, but these are omitted because they are not the gist of the present invention [7]. In addition, in the diagram, the division between the first and second phase single-output distillation columns and the first and second solvent pardoning columns is not necessarily clear and may be difficult to distinguish, so the following symbols are used in the diagram.

Symbol Process El 1st extractive distillation column EII 2nd Sl 1st solvent stripping column S11 2nd S Smelt] stripping column (shared with El and EII) Figure 1 shows the first extractive distillation process and the second extractive distillation process. This is an example in which solvent stripping towers are installed independently in columns 1-7. Feedstock hydrocarbons are fed through conduit 1 to a first extractive distillation column (El) 2, where they are extracted and distilled in the presence of a selective solvent fed through conduit 6, and from the top of the column are mainly paraffins and olefins hydrocarbons. The constituent fractions are discharged after 4 cycles,
From the bottom of the column, a stream consisting of hydrocarbons and solvents mainly composed of diolefins and acetylenes is sent via conduit 5 to the next first solvent stripping column (Sl) 6. A substantially hydrocarbon-free solvent is obtained from the bottom of the first solvent stripping column, and this stream is recycled via four pipes 6 to the first extractive distillation column.

On the other hand, from the top of the first solvent stripping column, a stream of hydrocarbons (which may contain a small amount of solvent) consisting of fins, acetylenes, etc. is obtained.

This stream passes through conduit 7 to a second extractive distillation column (lull) 8.
The diolefin "1" from which selective solvents, etc., which are supplied through conduit 9 and is substantially removed, is obtained through treatment 10, while from the bottom of the column, it is obtained mainly consisting of acetylenes, etc. and solvent. Flow is extracted via conduit 11 and this flow is then
It is sent to the solvent stripping tower (8+1) 12. The diolefins 1 obtained via the conduit 10 are optionally sent to a final purification step 4 (not shown), where they are loaded with high purity butadiene or inzolene (13). Second solvent release fl'1. Acetylenes, etc. are discharged from the top of the column via conduit 15, while from the bottom of the column, d
An essentially hydrocarbon-free solvent stream is obtained, which is recycled via line 9 to the second extractive distillation column 8. According to the present invention, the side stream extracted from the raw material supply stage of the second solvent stripping tower 12 via the conduit 14 gives heat to the object to be heated in the heat exchanger 15, condenses, and becomes a liquid stream, which is passed through the conduit 16. It is returned to the raw material supply stage of the stripping tower. When acetonitrile is used as the solvent, the column 12 usually has M plates of 10 to 30.
A reflux ratio at the top of the column of 10 to 20 is usually sufficient.

FIG. 2 shows an example of a process in which the first extractive distillation column and the first extractive distillation column share a solvent stripping column. In this process, the first solvent stripping column in FIG. 1 is omitted, the bottom liquid of the first extractive distillation column (El) 22 is directly supplied to the second extractive distillation column (Ell) 26, and a common bath is used. The substantially hydrocarbon stream obtained from the bottom of the agent stripping column (S) 30 via conduit 32 is divided into two parts, and a portion 14- is sent via conduit 23 to the first extractive distillation column. 22, the rest is conduit 2
7 to the second extractive distillation column 26. The method of extracting the side vapor stream from the raw t1 feed stage of the solvent stripping tower filter 0 and returning the transferred liquid stream that has been sent to the heat recovery stage is the same as that shown in FIG.

The figure shows another example in which the first extractive distillation column and the second extractive distillation column share the entire solvent stripping column. In the figure, feedstock hydrocarbon d is supplied to a first column (El) (first extractive distillation column) 42 through a conduit 41. The extractive distillation is carried out in the presence of a selective bath agent I, which is supplied via the 2s pipe 43, from columns n'i to i.
A fraction mainly consisting of paraffins and olefin hydrocarbons is discharged from the column 44 through a pipe 44, and a fraction mainly consisting of diolefins and acetylenes is discharged from the column 4 through a conduit 45. A stream consisting of hydrocarbons and bath agents is obtained, and this stream is
It is supplied to 1 part of 46 columns (functionally consisting of parts of the recovery sections of the first and second extractive distillation columns and 117 parts of the solvent stripping column in FIG. 1).

The bottom part of the column and the rest are connected to the second column (Ell) (second column) via conduit 49.
(extractive distillation column) 51. On the other hand, the selective solvent necessary for the operation of the second column is supplied to the upper part of the column through a conduit 52, and as a result, rholefins containing no acetylenes having the same number of carbon atoms as 7-tadiene or isoprene are produced with 4-terminals. A flow consisting of hydrocarbons relatively rich in acetylenes etc. and bath agents is obtained from the bottom of the column via conduit 56, and this stream (is obtained through conduit 45).
The 6th column VC is supplied to the 6th column via conduit 50.

From the bottom of the 64th column, a substantially hydrocarbon-containing solvent is obtained via line 55, this stream being split in two, a portion via line 43 to the first column 42 and the remainder via line 52. It is circulated to the tower 51 through the.

From the middle stage of the sixth column (this stage corresponds to the raw material supply stage of the solvent stripping tower), a rigid vapor flow consisting of a small amount of hydrocarbons rich in acetylenes and a large amount of solvent is passed through conduit 56. A part of the extracted part is directly sent to the bottom of the fourth column 61 via a conduit 57 in order to ensure a safe amount of steam for operation of the fourth column (S) 61 (consisting of the concentration section of the solvent stripping column). supplied,
The rest passes through four tubes 58, and a heat exchanger 59 for recovering heat IJ transfers heat to the fluid to be heated, and then condenses A11Sl~
A liquid stream is supplied to the bottom of the fourth column 61 via a conduit 60.

From the top of the fourth column, hydrocarbons rich in acetylene, etc. are first discharged to the outside through conduit 62, while from the bottom of the column, through conduit 5
From the vapor stream in 6) a) a stream of solvent with reduced hydrocarbon dust is obtained via 6, which stream is in the same stage as the stage from which conduit 5 of the third column is withdrawn. be returned.

In FIG. 3, the 11M part (S) of the third column 46 and the fourth
Together with the tower 61, they function as one solvent stripping tower.

In Figures 1 to 6, the flow of hydrocarbons is 4f 1
．． 21. 41 ノ＠ Fee Conduit 4,24.4
4 Nono Rough Inn 1f1, Olefin Noko 1-1 Two Conduit 10.28.53 Diolefin Conduit 13
．． 31.62 Acetylenes, etc. correspond.

The effect of the present invention is that by providing a heat recovery process for the side vapor stream extracted from the solvent stripping tower, the amount of heat can be effectively utilized, and the amount of heat that is exhausted from the column of the solvent stripping tower can be reduced. It is possible to save energy in the entire process by keeping it to a minimum of one stream.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 A mixed solvent of acel-nide IJ-water (weight ratio: 92:
8) was used to separate and purify phthanene from the C4 fraction.

The raw C4 fraction is passed through conduit 41 (the one in Figure 3,
(The same applies hereinafter) and was supplied to the column 42.

The operating conditions for 451, 46 and 61 were as follows.

18- Column 46 1 to 16 (from the sand grain) 56 takes out the measured vapor flow of the mixed solvent that passes through the acetylenes and 0. The remaining side vapor stream is passed through the heat exchanger 59, where the column is Diolefin IiC was taken out from the bottom of column 42 and was exchanged with the liquid mixed solvent stream, and then fed to the bottom of column 61 in the form of a hot surface. The columns 42 and 46 are equipped with an overhead condenser and a beam boiler at the bottom of the columns 42 and 46, respectively.

The flow rates in the main conduits were:

(Single q K sim) Since acetylenes are concentrated in the bath area of column 61, in order to avoid the risk of explosion due to self-decomposition k Although not shown in the figure, it was diluted with raffinate, an overhead byproduct of column 42, to improve safety.

Methods based on conventional technology (No. 6) in terms of effective energy use
When the heat recovery device 59 in the figure is not present) and the method of the present invention are applied to the column 61.
The ratio of the energy dissipated by condensation 21 of R and I to cooling water, etc. was as follows.

11- Conventional technology (without heat recovery process) QC=2.
555 x 10' K, cal/H Invention method QC = 1,000
] From this, it was found that the method of the present invention can actually save about 61% compared to the conventional technique σfir, and it is clear that the effect is remarkable.

Example 2 Follow the flow shown in Figure 6) 2l-1) Ru Allyl alcohol-water mixed solvent (weight ratio 75:15+10)
The case where inoprene is separated and purified from the C5i fraction using the method is shown.

Although not shown in the figure, raw material C obtained by naph cracking
The 5th fraction is heat-treated in advance to trimerize most of the 7 chlorine and ntadiene, and then 1 substance is separated in a pre-concentration column. It was supplied as a steam stream to the 54th stage from the bottom via the conduit 41. .

The operating conditions of columns 42, 51, 46 and 61 are as follows 22- It was as follows.

200th step from the bottom of tower 46 1. ! The side vapor stream of mixed M containing acetylenes, etc. is taken out by the + bone 56, the side vapor stream corresponding to the amount of heat commensurate with the reduction θIL required in the column 61 is removed, and the remaining side vapor stream is heated. It passed through an exchanger 59, where it exchanged heat with the planar mixed solvent stream taken out from the third stage from the bottom of the column 42, recovered the heat, and delivered it to the bottom of the column 61 in the planar form. .

In towers 42, 51 and 62, a rewheeler was installed at the bottom of towers 42 and 46, which were replaced by a slow-reduction of tower JF4.From the viewpoint of effective energy utilization, the method according to the prior art and the method of the present invention were combined. A comparison of the energy dissipated by cooling water and the like in the condensers of tower 61 and tower 1n was as follows.

Conventional technology (1 case without heat recovery process) Qc = 2
22.000 (Tcal, /II) The method of the present invention Qc2 61.000 (Tea'j/'TI) From this, it can be seen that the method of the present invention saves 76% compared to the conventional technology. It became clear that this was significant.

25-

[Brief explanation of drawings]

FIG. 1 is a flow sheet of one embodiment of the method of the present invention, and FIGS. 2, 6, 4, and 5 are flows of another embodiment. 1, 21.41... Raw material conduit 4, . 24.44...Nonorafuinji, olefin conduit 10.28.53...Georefuis frequent conduit 13.3
1.62...Acetylene forward ring conduit 2, 22.42 (g
l)...First extractive distillation column 8, 26.51 (Eu).
...Second extractive distillation column 6 (81)...First solvent stripping column, a
(El)...Second solvent stripping tower 30, 61(S)...
・Solvent release tower 15, 34.59...Heat exchanger 3, 5.7.9.11.14, 16.26.25.27
．． 29.32°33, 35.43.45.47.48.
49.50.52.54.55゜56, 57.5B,,
60.63... Conduit 4υo Kff'lr-(y Zhu warehouse (26- Fig. 4 Fig. 5

Claims (3)

[Claims] (1) 2-Methyl-1,3-butadiene was grown from a hydrocarbon mixture of 0.4 liters of SiC to 2-methyl-1,3-butadiene of pure purity by a two-stage extractive distillation process in the presence of a selective solvent. At this time, a small amount of 1,6-butadiene or 2 is contained in the bottom liquid taken out from the extractive distillation column.
- In the process of separating acetylenes and/or 7-group hydrocarbons having the same carbon number as methyl-1,3-butadiene from a solvent stripping tower, steam is supplied from a stage near the raw material supply stage of the solvent stripping tower. supplying the side stream consisting of the selective solvent referring to acetylenes and/or arenes extracted as a phase to a heat recovery step and then returning it to a stage adjacent to the withdrawal stage of the side stream of the solvent stripping column; A method for efficiently separating and purifying 1,3-butadiene or 2-methyl-1,3-butadiene from Ca and id'c5 hydrocarbon mixture %+ characterized by (2) The method according to claim (1), wherein the heat recovery step is a side reboiler spanning a glue boiler at the bottom of the first extractive distillation column or at a stage near the bottom of the first extractive distillation column. (3) 1, where the heat recovery step is supplied from the first extractive distillation column;
Submission of hydrocarbons rich in 6-butadiene or 2-methyl-1,6-butadiene to the second extractive distillation column! @The method according to claim (1), which is a side reboiler in stages across stages and stages in the vicinity thereof.