DE102017114902A1 - IMPROVED METHOD AND APPARATUS FOR SEPARATING C4 CARBON HYDROCARBONS BY EXTRACTIVE DISTILLATION - Google Patents

Abstract

The present invention relates to a process for the separation of C-hydrocarbons by extractive distillation in which the C-hydrocarbons of a two-stage separation comprising (i) fractionation of the C-hydrocarbons into a light fraction and a heavy fraction, and (ii) extractive distillation the light fraction and / or the heavy fraction are subjected. The process described has the advantage over the prior art processes, especially when using feed mixtures rich in n-butane and 1-butene / isobutene, that reduced solvent circulation rates can be realized, which despite the additional process step leads to a lower energy consumption of the process. The present invention further relates to plants for carrying out such a process and the use of a separation sequence with the process steps (i) and (ii) for the separation of C-hydrocarbons, in particular when using feed mixtures rich in n-butane and 1 -Buten / Isobutene are.

Description

The present invention relates to a process for the separation of C ₄ -Stoffströmen by extractive distillation, which in addition to the extractive distillation itself includes a preceding this stage of fractionation of C ₄ hydrocarbons in a light fraction and a heavy fraction. As a result of this prefractionation, substances which are difficult to separate in an extractive distillation, such as in particular 1 -Buten / isobutene and n-butane, are separated before the extractive distillation, which in particular in feed mixtures for C ₄ separation, rich in n-butane and 1 -Buten / isobutene, with the advantage of a reduced solvent requirement in the separation is connected.

State of the art

The term "C ₄ streams" refers to mixtures of hydrocarbons with predominantly 4 (four) carbon atoms per molecule, ie mixtures whose main components are compounds with 4 Carbon atoms per molecule (ie, more than 85 wt .-% of the mixture, in particular at least 95 wt .-% of the mixture, typically more than 98 wt .-% of the mixture), which in addition also contain small amounts of compounds in these mixtures for example, hydrocarbons having three or five carbon atoms per molecule. C ₄ streams are obtained, for example, in the production of ethylene and / or propylene by thermal or catalytic cracking of a petroleum fraction such as liquefied petroleum gas, mineral spirits or gas oil. Furthermore, C ₄ -offstream streams are obtained in the catalytic dehydrogenation of n-butane and / or n-butene and in the selective hydrogenation of 1,3-butadiene.

C ₄ streams generally contain n-butane, isobutane, isobutene, 1-butene and cis- / trans- 2 Butene, 1,3-butadiene, 1,2-butadiene and butene, in particular 1 Butyne (ethyl acetylene), and butenine (vinyl acetylene). In addition, C ₄ -stoff streams may also have low levels of cyclobutane.

C ₄ fluid streams from fluid catalytic cracking (FCC) and steam cracking (SC) usually consist of two butane isomers (isobutane and n-butane), four butene isomers (isobutene, 1-butene and cis- and trans- 2 Butene) and 1,3-butadiene as main components. In addition to 1,3-butadiene, which is an important starting material for synthetic rubber, especially the butene isomers of economic importance, since they can be converted eg by reaction of isobutene with methanol to methyl tert-butyl ether (MTBE) or by dehydrogenation and optionally double bond isomerization of n-butenes ( 1 -Buten and 2 Butenes) can be converted to 1,3-butadiene. n-butenes are also starting material for 2 Butanol, which is often further dehydrogenated to methyl ethyl ketone (MEK).

In addition, can 1 Be used as a monomer for the preparation of LDPE and LLDPE or processed via a dimerization to octene. Another important industrial product, characterized by oxidation 1 Butene or n-butane can be prepared is maleic anhydride.

However, the separation of butane and butene in such a mixture is not possible with conventional separation processes, such as distillation, because of the relatively close boiling temperatures (see Table 1). Table 1: Normal boiling points of the C ₄ components C4 component NBP * [° C] isobutane -11.7 1-butene -6.3 isobutene -6.9 1,3-butadiene -4.4 n-butane -0.5 2-trans-butene +0.9 2-cis-butene +3.7 * Normal boiling point

By "superimposed boiling temperature" is meant, for example in the case of n-butane / butene isomers, that the component n-butane has a boiling point which is between the boiling temperatures of the butenisomers. In contrast, isobutane boils at a lower boiling temperature than all butene isomers. As a result, isobutane and n-butane (together as a butane fraction) can not be separated from the mixture at once by distillation.

For the separation of butenes from C ₄ streams, one can take advantage of the phenomenon that the various C ₄ components dissolve differently in certain polar solvents. This phenomenon was initially used in the extraction process for the separation of butane and butene, which was later developed to extractive distillation.

The Uhde Butenex ^® process is an extractive distillation process using a mixture of n-formylmorpholine (NFM) and morpholine (MOR) as the solvent. Since n-butane and isobutane do not dissolve significantly in this solvent, they can be separated off as the top product of the extractive distillation, while the butenes dissolved in the solvent mixture can be further transferred as bottom product to a recovery column in which the solvent and butene fraction are separated again. The recovery column can be designed, for example, as a stripping column.

A weak point of the conventional extractive distillation process, however, is that in certain compositions of the C ₄ starting material the extractive distillation process is associated with relatively high energy requirements. As a result, the separation process is not economical for certain applications because high solvent cycles are required to achieve the desired product specifications. This weakness arises especially in cases where high product yields are desired. Here, for C ₄ starting materials with a high proportion of n-butane, 1-butene and optionally isobutene (ie 30 wt.% Or more) and a high proportion of n-butane (more than 20 % By weight, based on the total amount of n-butane, 1-butene and isobutene), large solvent recycle rates are required to achieve over 90% yield with moderate product purity. If, in addition, a high purity, eg of 99%, is sought for such starting materials, the necessary solvent circulation rate becomes even greater.

This could be due to the fact that n-butane behaves as a high boiler to most butene isomers, which makes setting the process parameters to obtain n-butane together with isobutane as the top product of the extractive distillation column difficult.

Compared to n-butane, 1-butene, on the other hand, constitutes a low-boiling component and can only be realized with the aid of solvent as the bottom product of the extractive distillation column. In the sequence is a C ₄ -Feed (ie one fed to the process C ₄ starting material) having a relatively high proportion of n-butane or 1 Buten "unfavorable" for the process, because per amount used relatively more solvent for the separation is needed.

From the above, there is a need for a process in which relatively low solvent recycle rates can be realized independently of the butane and especially the n-butane content of a C ₄ feed and independently of the butene composition of the C ₄ product. The above invention addresses this need.

Description of the invention

1. (i) Fraktionierung der C₄-Kohlenwasserstoffe in eine Leichtfraktion und eine Schwerfraktion, und
2. (ii) extraktive Destillation der Leichtfraktion und/oder der Schwerfraktion,

unterworfen werden.According to a first aspect, the present invention relates to a process for the separation of C ₄ -hydrocarbons by extractive distillation, which is characterized in that the C ₄ -hydrocarbons of a two-stage separation comprising

1. (i) fractionating the C ₄ hydrocarbons into a light fraction and a heavy fraction, and
2. (ii) extractive distillation of the light fraction and / or the heavy fraction,

be subjected.

If in the above by a light fraction and a heavy fraction are mentioned, as the lower boiling components to consider this is the C ₄ hydrocarbons on the one hand (light fraction) and the higher-boiling constituents of the C ₄ hydrocarbons consider other (heavy fraction) denote. The data "lower boiling" and "higher boiling" indicate a lower or higher boiling point compared to other constituents of the C ₄ hydrocarbons.

In a preferred embodiment, the light fraction preferably comprises isobutane and 1 Butene / isobutene. Accordingly, the heavy fraction preferably comprises n-butane and 2 Butenes. The light fraction preferably comprises C ₄ hydrocarbons having a boiling point (NBP) below -2 ° C. The heavy fraction according to the present invention preferably comprises C ₄ -hydrocarbons having a boiling point (NBP) of more than -2 ° C. The term "NBP" refers here in the general technical understanding of the "normal boiling point" at a pressure of 101.3 kPa.

The term "n-butene" below refers to linear butenes including 1-butene, 2-cis-butene and 2 but not the nonlinear isobutene. The term "butene", however, includes all butenisomers, linear butene as well as non-linear and cyclic butene.

If percentages are referred to in the present invention, this shall be construed as a percentage by mass, unless otherwise specified.

When "solvent" is mentioned below in connection with the extractive distillation, this term also includes mixtures of solvents unless expressly stated otherwise.

The fractionation of the C ₄ hydrocarbons into a light fraction and a heavy fraction can be carried out according to standard methods for the distillative separation of C ₄ hydrocarbon fractions. The distillative separation can be carried out in apparatuses commonly used for the separation of such hydrocarbon mixtures. Such apparatuses include, for example, distillation or fractionation columns.

The separation is preferably carried out in a superfractionation column. The feed to this column is preferably in the lower half, preferably in the lower third of the column. Because of the close boiling position of the mixture to be separated, the column preferably 20 or more, preferred 35 or more, and more preferably 45 or more theoretical plates. On the other hand, the separation with more than 120 Separators no longer significantly better, so that as a reasonable upper limit for the number of separation stages a number of 120 , especially 100 and preferred 90 can be specified. Most preferably, the separation column has approximately 50 to 80 theoretical plates on. The reflux ratio (amount of reflux to distillate decrease), depending on the realized number of stages and the operating pressure, preferably ≤ 20, preferably <16, and particularly preferably <14. The reflux ratio should on the other hand at least 2 , and preferably at least 3 be. Particularly suitable for the reflux ratio may be a range of about 4 to 12 The condensation can be carried out against cooling water or air.

The distillate container is preferably designed as a liquid-liquid separator. As a result, any water contained in the feed stream can optionally be separated off as the second phase in the distillate vessel, and a technically anhydrous bottom product can be obtained.

The separation in the fractionation of the C ₄ hydrocarbons into a light fraction and a heavy fraction is preferably carried out at a pressure of 4 to 12 bar absolute (bara), preferably at a pressure of 5 to 8th bara, performed. The temperature at which the separation is carried out is preferably 35 to 80 ° C, preferably 40 up to 60 ° C.

To heat the evaporator of the column, a conventional heat transfer medium, such as steam or hot water, and preferably waste heat from other processes can be used. In the latter case, it may be advantageous to equip the column with more than one evaporator. The column is preferably equipped as a simple column with at least one evaporator and at least one condenser. Because of the high energy demand and the small temperature difference between the bottom and top of the column energy saving circuits are particularly preferred embodiments. As an example, the method of vapor compression is mentioned here.

Another particularly preferred circuit is a double-pressure distillation (double effect distillation) in integration with a second column. The second column may preferably have a downstream column be the same or different separation task. In this case, one of the columns is operated at such a high pressure that their condensation temperature is sufficient to heat the other column.

In the extractive distillation of the light fraction and / or heavy fraction (step (ii)), it is preferred to include n-formylmorpholine (NFM) as the main solvent. The term "main solvent" has the meaning that the n-formylmorpholine represents the largest mass percentage of the solvent in the extractive distillation, ie at least a mixture of two solvents 50 Percent by mass of the total solvent and in a mixture of three solvents, the highest percentage by mass of the components involved. The main solvent can also make up 100% of the solvent used.

Optionally, the principal solvent may be combined with one or more co-solvents. A suitable co-solvent is, for example, morpholine. However, the process according to the invention is not restricted to the use of these solvents or of this mixed solution, so that other solvent mixtures, such as, for example, n-formylmorpholine mixed with methyl ethyl ketone (MEK) or n-formylmorpholine in admixture with N, N'-diformylpiperazine (DFP ) can be included in step (ii) of the method according to the invention. Another useful solvent is N-methylpyrrolidone (NMP) or N-ethylpyrrolidone (NEP) or a mixture of NMP and NEP. It is likewise possible to use acetonitrile, dimethylformamide or hexane with the admixture of dimethylformamide as solvent, as described in US Pat EP 0 505 238 B1 or the prior art given there.

Suitable C ₄ feeds which can be included in the process according to the invention are, as indicated above, above all C ₄ -hydrocarbon streams from the fluid catalytic cracking (FCC) and steam cracking (SC). Exemplary compositions of such C ₄ fuel streams are given in the following table: C4 component SC FCC [Wt .-%] [Wt .-%] 1,3 butadiene 35-50 0-0.5 isobutene 15-30 10-25 2-cis-butene 5-10 10-20 2-trans-butene 5-10 10-20 1-butene 5-20 10-25 isobutane 1-5 20-40 n-butane 1-10 10-20

If the C ₄ feed contains significant levels of butadiene, these may be removed from the mixture as needed before feeding the feed into the process of the present invention. A suitable process which can be used for this purpose is, for example, an extractive distillation for butadiene recovery or a selective hydrogenation for the conversion of butadiene 1 -Buten and 2 Butene. If necessary, isobutene can be removed beforehand by etherification, eg MTBE synthesis.

As described above, with the process according to the invention, the energy requirement for the separation of C ₄ -hydrocarbons rich in n-butane and 1 -Buten / isobutene, are significantly reduced. For the process according to the invention, it is correspondingly preferred if the C ₄ hydrocarbons which are included as feed in the process, a proportion of at least 30 Wt .-% and preferably more than 50 Wt .-% of n-butane, 1-butene and isobutene based on the feed amount and wherein the n-butane content, based on the total amount of n-butane, 1-butene and isobutene in the range of 20 to 80 Wt .-% and preferred 40 to 60 % By weight.

For a conventional separation process, the energy demand is highest when n-butane and 1 Butylene / isobutene in the mixture to be separated in a ratio of about 1: 1. In the context of the described invention, therefore, particularly large energy savings can be realized when the ratio of butane and 1 -Butene / isobutene in the range from 2: 1 to 1: 2 and in particular 1.5: 1 to 1: 1.5. C ₄ -hydrocarbons which fulfill these requirements are therefore particularly preferred in the context of the present invention.

Another aspect of the present invention relates to a plant for the separation of C ₄ hydrocarbons, which comprises a device for separating the C ₄ hydrocarbons into a light fraction and a heavy fraction, at least one downstream of this device distillation column for an extractive distillation and at least one of the distillation column downstream device for the separation of C ₄ hydrocarbons from the solvent used in the extractive distillation has.

For preferred embodiments of the device for the separation of the C ₄ hydrocarbons into a light fraction and a heavy fraction, reference may be made to the above statements on the method according to the invention.

In the distillation column for the extractive distillation, the C ₄ -hydrocarbons are brought into contact with a solvent mixture, so that the unsaturated constituents dissolve in the solvent and can be separated off as the bottom product. Saturated C ₄ hydrocarbons, however, can be separated from the gas phase of the extraction process (overhead product).

In the distillation column for the extractive distillation downstream device for the separation of C ₄ hydrocarbons from the solvent used in the extractive distillation, the C ₄ hydrocarbons are expelled, for example, by reducing the pressure from the solvent. For this purpose, it may be useful if the device for separating C ₄ hydrocarbons from the solvent used in the extractive distillation an evaporator is followed, which is operated at a pressure P _2, which is lower than the pressure P ₁ in the sump of the device for the separation of C ₄ hydrocarbons from the solvent used in the extractive distillation, wherein the vapors leaving the evaporator are condensed, collected and recycled to the C ₄ hydrocarbon removal device from the solvent used in the extractive distillation while the solvent withdrawn in the liquid state from the bottom of the evaporator and is returned to the distillation column for an extractive distillation. Corresponding devices are for example in the DE 41 31 938 A1 described.

In a particularly preferred first embodiment of the system according to the invention, these supply lines for the light fraction and the heavy fraction to respective distillation columns for extractive distillation of the light fraction and the heavy fraction, wherein the distillation columns for extractive distillation respectively devices for the separation of C ₄ hydrocarbons from in the extractive distillation solvents used are downstream in the flow direction. Accordingly, this embodiment of the plant comprises two distillation columns for extractive distillation and two devices for the separation of C ₄ hydrocarbons from the solvent used in the extractive distillation.

Alternatively, the plant in a second preferred embodiment, supply lines for the light fraction and heavy fraction and to respective distillation columns for extractive distillation, but the distillation columns for extractive distillation transfers to a common device for the separation of C ₄ hydrocarbons from that in the extractive distillation have used solvents. While this embodiment has the advantage over the above that less apparatus construction is required, it has the disadvantage that a mixture of all butene isomers is inevitably obtained as a product. The former embodiment, however, provides butene products by 1 -Butene and isobutene spatially separated from 2 -Butenes (cis and trans) are obtained.

In an alternative to the third preferred embodiment, the plant according to the present invention, reservoir, preferably two reservoirs, which are connected downstream of the device for separating the C ₄ hydrocarbons in a light fraction and a heavy fraction in the flow direction and which consequently the light fraction and the heavy fraction be forwarded. Of these storage containers should be at least one flowable, in particular open, connected to a device for extractive distillation. Preferably, the system has supply lines from the storage containers in the device for extractive distillation, which are connected controllable by appropriate flow devices, for example in the form of valves, valves or taps, so that in the system as needed, either the supply line from the first reservoir or the supply line is opened from the second reservoir.

This embodiment has the advantage that it allows a semi-continuous process, wherein the light fraction and the heavy fraction from the fractionation of C ₄ hydrocarbons are stored first in the reservoirs, and, as needed, the distillation column for an extractive distillation and this in the flow direction downstream device for the separation of C ₄ hydrocarbons can be supplied from the solvent used in the extractive distillation. Since the process control is comparable in terms of the solvent used and the process conditions for the heavy fraction and the light fraction, so the same distillation column and apparatus for downstream separation of C ₄ hydrocarbons from the solvent used in the extractive distillation for the separation into the final products be used.

By using a heat pump system, the energy requirements for the C ₄ hydrocarbon separation apparatus can be minimized to a light fraction and a heavy fraction. It is therefore preferred for the system according to the invention if the device for separating the C ₄ hydrocarbons into a light fraction and a heavy fraction has a heat pump system. An example of a suitable heat pump system is based on the compression of the overhead vapors. In this case, the fractionation column is followed by a compressor, with which the light fraction is compressed and thereby further heated. After compression, the light fraction is cooled to a liquid product by, in turn, transferring heat to evaporate the heavy fraction in a reboiler of the fractionating column. Both the part of the heavy fraction heated in the heat exchanger and part of the light fraction (column reflux) cooled in the heat exchanger are then passed back into the fractionating column.

Another aspect of the present invention relates to the use of a separation sequence comprising a fractionation of C ₄ hydrocarbons into a light fraction and a heavy fraction and an extractive distillation of the light fraction and / or the heavy fraction, the C ₄ hydrocarbons having a proportion of at least 30 Wt .-% and preferably more than 50 Wt .-% of n-butane, 1-butene and isobutene and wherein the n-butane content, based on the total weight of n-butane, 1-butene and isobutene in the range of 20 to 80 Wt .-% and preferred 40 to 60 % By weight.

The process according to the invention and the plants described are particularly suitable for the separation of "unfavorable" for the extractive distillation starting materials (with original high solvent circulation), since in these the energy consumption of the separation process can now be significantly reduced due to the lower solvent circulation rates.

list of figures

• 1 shows a plant according to the first preferred embodiment, as described above, in the apparatus for separating the C ₄ hydrocarbons into a light fraction and a heavy fraction 1 two distillation columns for extractive distillation 2 . 3 and these distillation columns are each devices for separating the C ₄ hydrocarbons from the solvent used in the extractive distillation 4 . 5 are downstream. About the supply lines 6 and 7 becomes the light or the heavy fraction of the device 1 to the devices 2 and 3 directed. From these devices escapes the overhead product on the derivatives 8th and 9 while the bottoms product over the transitions 10 and 11 in respective devices for the separation of C ₄ hydrocarbons from the solvent used in the extractive distillation 4 . 5 is transferred. The solvent recovered via this process is then passed through the lines 14 . 15 back to the distillation columns for extractive distillation 2 . 3 while the C ₄ hydrocarbon fractions liberated from the solvent pass through the effluents 12 and 13 be derived.
• 2 shows a plant according to the preferred second embodiment of the present invention described above, this apparatus being one for the extractive distillation 2 . 3 common device for the separation of C ₄ hydrocarbons from the solvent used in the extractive distillation 4 having.
• 3 shows finally a system according to the third preferred embodiment described above, the apparatus for separating the C ₄ hydrocarbons into a light fraction and a heavy fraction 1 downstream reservoir 16, 17 has. In 3A is the reservoir 16 via a supply line 6A with the device for extractive distillation 2 connected. In 3B is alternatively the reservoir 17 via the supply line 7A with the device for extractive distillation 2 connected. As can be seen from the drawing, the corresponding device expediently both leads from the reservoir 16, as well as from the reservoir 17 in the device for extractive distillation 2 on, which are controllably connected by respective valves, so that in the device as needed, either the supply line 6A or the supply line 7A to be open.

In the following, the present invention will be further illustrated by way of examples, which, however, are not intended to be in any way material to the evaluation of the scope of the present invention.

Examples:

The following table illustrates how the normal boiling points of the butane isomers change by the addition of NFM / MOR as the solvent. C4 component NBP * [° C] NBP [° C] in NFM / MOR * isobutane -11.7 -11.7 1-butene -6.3 about +10 isobutene -6.9 about +7 1,3-butadiene -4.4 approx. +12 2-trans-butene +0.9 approx. +16 n-butane -0.5 -0.5 2-cis-butene +3.7 approx. +21 * NFM / MOR = 1: 1

It can be seen from the table that all butene isomers in an NFM / MOR solvent mixture have higher boiling points than the butane isomers. Nevertheless, the boiling points of isobutene (about + 7 ° C) and n-butane (-0.5 ° C) are still quite close to each other. In a first step, the C ₄ components are separated into a heavy fraction (n-butane and 2 Butene-isomers) and a light fraction (isobutane, 1-butene, isobutene and 1,3-butadiene), so there is a boiling point difference between isobutane and the butene isomer with the lowest boiling point (isobutene) of about 19 ° C in the subsequent extractive distillation of the light fraction. For the heavy fraction, there is a minimal boiling point difference between n-butane and butene isomers of about 16 , 5 ° C. This results in lower solvent requirements to achieve similar specifications in terms of purity or yield.

Example 1:

In the following, a theoretical calculation of the energy balance of a conventional separation (only extractive distillation) was carried out compared to a separation with a pre-separation upstream of the extractive distillation. The underlying C ₄ feed composition contained about 57% by weight of n-butane, butene 1 and isobutene, with n-butane being about 40 Wt .-% of the total amount of n-butane, butene 1 and isobutene. The underlying composition is as follows: 1,3 butadiene 0.1% by weight isobutene 1.6% by weight 2-cis-butene 13.2% by weight 2-trans-butene 18.0% by weight 1-butene 31.9% by weight isobutane 12.0% by weight n-butane 23.2% by weight

Process performance:

The introduced specific effort index is a measure of the demand for operating resources (steam, cooling water, electricity) and is thus relevant for both OPEX and CAPEX. CONV invention Improvement / savings specific effort index 100 62.5 - 37.5% Products (absolutely) Butane yield 0.95 0.98 + 0.03 Butane purity 0.78 0.90 + 0.12 Butene yield 0.85 0.90 + 0.05 Butene purity 0.97 0.99 + 0.02 Equipment [normalized] (relative) cooling water 100 67 - 33.3% HD steam (230 ° C for stripper) 1:50 0.65 - 55.5% MD steam (160 ° C for ED) 0.80 0.65 - 18.8% ND steam (80 ° C for pre-column) 00:00 0.60 n / A HD + MD steam 30.2 1.30 - 42.5% Steam sum (HD + MD + ND) 30.2 1.90 - 16%

Compared with the conventional distillation process without preliminary separation (KONV), in which butanes and butenes can be separated only with great effort, the inventive method (invention) with pre-column with moderate effort significantly better process performance (ie, a better product yield and higher product purity ).

The steam and cooling water consumption are also lower in the process according to the invention. Furthermore, the high pressure (HD) and medium pressure (MD) steam consumption are significantly reduced. The additionally required in the process according to the invention low pressure (LP) vapor is less valuable than the HD or MD steam and as the process dissipated steam (Abdampf) often already exist. In addition, the consumption can be further reduced by various heat integration options.

LIST OF REFERENCE NUMBERS

1

Separator of C ₄ hydrocarbons in light and heavy fraction

2

Apparatus for extractive distillation

3

Apparatus for extractive distillation

4

Device for the separation of C ₄ -hydrocarbons from the solvent used in the extractive distillation

5

Device for the separation of C ₄ -hydrocarbons from the solvent used in the extractive distillation

6

supply

6A

supply

7

supply

7A

supply

8th

Derivation for top product

9

Derivation for top product

10

reconciliation

11

reconciliation

12

Derivation of C ₄ -hydrocarbons from the bottom product

13

Derivation of C ₄ -hydrocarbons from the bottom product

14

Line for the return of solvent

15

Line for the return of solvent

16

reservoir

17

reservoir

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0505238 B1 [0027]
• DE 4131938 A1 [0035]

Claims (11)

Process for the separation of C ₄ -hydrocarbons by extractive distillation, characterized in that the C ₄ -hydrocarbons of a two-stage separation comprising (i) fractionating the C ₄ hydrocarbons into a light fraction and a heavy fraction, and (ii) extracting the light fraction and / or the heavy fraction are subjected. Method according to Claim 1 wherein the light fraction comprises isobutane and 1-butene, optionally isobutene. Method according to Claim 1 or 2 wherein the heavy fraction comprises n-butane and 2-butene. Method according to claim one of Claims 1 to 3 wherein N-formylmorpholine is included as the main solvent optionally with one or more co-extractants in the extractive distillation. A process according to any one of the preceding claims, wherein the C ₄ hydrocarbons have a content of at least 30% by weight and preferably more than 50% by weight of n-butane, 1-butene and isobutene and where the n-butane content is based on the total weight of n-butane, 1-butene and isobutene, in the range of 20 to 80 wt .-% and preferably 40 to 60 wt .-%. Plant for the separation of C ₄ -hydrocarbons, comprising an apparatus for separating the C ₄ hydrocarbons into a light fraction and a heavy fraction, at least one downstream of this device distillation column for extractive distillation using a solvent or solvent mixture and at least one of the distillation column in Flow direction downstream device for the separation of C ₄ hydrocarbons from the solvent or solvent mixture used in the extractive distillation. Appendix according to Claim 6 , characterized in that it has feed lines for the light fraction and the heavy fraction to respective devices for extractive distillation, and that the devices for extractive distillation respectively downstream of devices for the separation of C ₄ hydrocarbons from the solvent or solvent mixture used in the extractive distillation in the flow direction are. Appendix according to Claim 6 characterized in that it comprises feed lines for the light fraction and the heavy fraction to respective extractive distillation apparatuses, and that the extractive distillation means provide transfers to a common means for separating C ₄ hydrocarbons from the solvent or mixture of solvents used in the extractive distillation exhibit. Appendix according to Claim 6 , characterized in that the device for the separation of the C ₄ hydrocarbons in a light fraction and a heavy fraction are connected downstream of reservoir, of which at least one is fluidly connected to a device for extractive distillation. Annex according to one of the Claims 6 to 9 , characterized in that the device for separating the C ₄ hydrocarbons into a light fraction and a heavy fraction comprises a heat pump system. Use of a separation sequence comprising a fractionation of the C ₄ hydrocarbons into a light fraction and a heavy fraction, and an extractive distillation of the light fraction and / or the heavy fraction for the separation of C ₄ hydrocarbons, which account for at least 30% by weight and preferably more having 50 wt .-% of n-butane, 1-butene and isobutene and wherein the n-butane content, based on the total weight of n-butane, 1-butene and isobutene, in the range of 20 to 80 wt .-% and preferably 40 to 60 wt .-% is.

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