U.S. patent application number 16/250811 was filed with the patent office on 2019-05-23 for method of separating normal butene using isomerization and process system for separating normal butene.
The applicant listed for this patent is LG CHEM, LTD.. Invention is credited to Soo Hwan HWANG, Dae Hyeon KIM, Jeong Seok LEE, Jong Ku LEE.
Application Number | 20190152878 16/250811 |
Document ID | / |
Family ID | 57248111 |
Filed Date | 2019-05-23 |
United States Patent
Application |
20190152878 |
Kind Code |
A1 |
KIM; Dae Hyeon ; et
al. |
May 23, 2019 |
METHOD OF SEPARATING NORMAL BUTENE USING ISOMERIZATION AND PROCESS
SYSTEM FOR SEPARATING NORMAL BUTENE
Abstract
Provided are a separation system for easily recovering normal
butene from an olefin fraction including isobutene, isobutane,
1-butene, 2-butene, and normal butane, and a separation process
system using the method. Since the separation system may easily
convert 1-butene included in the olefin fraction to 2-butene,
normal butene may be effectively separated and recovered by
factional distillation and each recovered fraction may be easily
refluxed even if the use of a reflux system using a refrigerant is
reduced or excluded. Thus, economic efficiency may be improved and
simultaneously, separation efficiency may be increased.
Inventors: |
KIM; Dae Hyeon; (Daejeon,
KR) ; HWANG; Soo Hwan; (Daejeon, KR) ; LEE;
Jong Ku; (Daejeon, KR) ; LEE; Jeong Seok;
(Daejeon, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG CHEM, LTD. |
Seoul |
|
KR |
|
|
Family ID: |
57248111 |
Appl. No.: |
16/250811 |
Filed: |
January 17, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15325329 |
Jan 10, 2017 |
10227270 |
|
|
PCT/KR2016/004459 |
Apr 28, 2016 |
|
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16250811 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02P 30/40 20151101;
B01D 3/007 20130101; Y02P 30/48 20151101; C07C 7/04 20130101; C07C
5/2556 20130101; B01D 3/009 20130101 |
International
Class: |
C07C 5/25 20060101
C07C005/25; B01D 3/00 20060101 B01D003/00; C07C 7/04 20060101
C07C007/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 13, 2015 |
KR |
10-2015-0066867 |
Claims
1. A separation system for recovering normal butene from an olefin
fraction, the separation system comprising: a supply unit that
supplies a reactant including an olefin fraction; a processing unit
connected to the supply unit, in which a single distillation column
is disposed, the distillation column including: at least one
isomerization reaction zone; at least one distillation zone; an
overhead discharge line; and a bottom discharge line; and a
recovery unit that is connected to the processing unit and recovers
a reaction product, the recovery unit comprising a heat exchanger,
a top fraction recovery unit connected to the overhead discharge
line of the distillation column to recover a top fraction, and a
bottom fraction recovery unit connected to the bottom discharge
line of the distillation column to recover a bottom fraction, the
heat exchanger refluxing each of the top fraction and the bottom
fraction without the use of a separate reflux system comprising a
condenser and reboiler.
2. The separation system of claim 1, wherein the supply unit
comprises a supply line which transfers the reactant to the
processing unit, and the supply line is connected to a stream in
which a C4 residue is recovered from naphtha cracking.
3. The separation system of claim 1, wherein the supply unit
further comprises a hydrogen supply line that supplies hydrogen to
the processing unit.
4. The separation system of claim 1, wherein the isomerization
reaction zone is located in top 5% to 50% of a total height of the
distillation column.
5. The separation system of claim 1, wherein the top fraction
recovery unit comprises a first reflux line that reintroduces at
least a portion of the top fraction into the processing unit, and
the bottom fraction recovery unit comprises a second reflux line
that reintroduces at least a portion of the bottom fraction into
the processing unit.
6. The separation system of claim 5, wherein: the recovery unit
further comprises a compressor and a reflux drum; the first reflux
line is sequentially connected to the compressor, the heat
exchanger, the reflux drum, and the processing unit, and the second
reflux line is sequentially connected to the heat exchanger and the
processing unit.
7. The separation system of claim 6, wherein: the compressor
compresses at least a portion of the top fraction to yield a
compressed top fraction; and the heat exchanger performs heat
exchange between at least a portion of the compressed top fraction
transferred through the first reflux line and at least a portion of
the bottom fraction transferred through the second reflux line,
refluxing each of the top fraction and the bottom fraction without
the use of a separate reflux system comprising a condenser and
reboiler.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of co-pending, allowed U.S.
patent application Ser. No. 15/325,329, which is a National Stage
Entry of International Application No. PCT/KR2016/004459, filed on
Apr. 28, 2016, and claims the benefit of Korean Patent Application
No. 10-2015-0066867, filed on May 13, 2015, in the Korean
Intellectual Property Office, the disclosure of each which is
incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] The present invention relates to a separation method for
easily recovering normal butene from an olefin fraction including
isobutene, isobutane, 1-butene, 2-butene, and normal butane, and a
separation process system for separating normal butene.
BACKGROUND ART
[0003] The annual 1-butene demand growth rate has been 3% to 4%,
and 1-butene is being used as a monomer for copolymerization of
high density polyethylene (HDPE) or linear low density polyethylene
(LLDPE). Recently, the price of 1-butene has been increased due to
a supply and demand imbalance caused by an increase in the price of
naphtha and a decrease in the utilization rate of naphtha cracking
process due to high oil price.
[0004] A C4 residue generally obtained from the naphtha cracking
process is composed of butadiene, isobutene, 1-butene, 2-butene,
normal butane, and isobutane, and a fraction, in which butadiene is
separated from the C4 residue, is referred to as "C4 residue I"
(mixture of isobutene, 1-butene, 2-butene, butane, and isobutane).
A fraction separated after isobutene is reacted with methanol to
prepare methyl tertiary butyl ether (MTBE) is referred to as "C4
residue II" (mixture of 1-butene, 2-butene, butane, and isobutane).
Also, a fraction, in which a trace of butadiene is removed by
introducing the C4 residue II into a selective hydrogenation
reactor, is referred to as "C4 residue 2.5".
[0005] In general, the production of 1-butene is performed in such
a manner that a fraction remaining after separating isobutene from
the C4 residue 2.5 is introduced into a distillation column to
obtain 1-butene having a purity of 99% or more from the top of the
column, and a C4 residue III, as a mixture of 1-butene, 2-butene,
and normal butane, is obtained from the bottom of the column. The
C4 residue III, with an overhead fraction of the isobutane
distillation column, is prepared into liquefied petroleum gas (LPG)
by a hydrogenation reaction. Also, the C4 residue III is separated
into olefin and paraffin, and the olefin is concentrated to a
concentration of 98 wt % of more and is then used to prepare methyl
ethyl ketone (MEK) or prepare 1,3-butadiene by oxidative
dehydrogenation. Furthermore, 1-butene and 2-butene are used to
generate propylene through an exchange reaction or may be used to
generate ethylene and hexane through an exchange reaction. In this
case, in order to economically utilize the C4 residue II and the C4
residue III, 1-butene and 2-butene must be recovered from the
resides (C4 residue II and C4 residue III) as much as possible, but
since boiling points of the 1-butene and the 2-butene contained in
the residues are very similar, it may not be possible to separate
the 1-butene and the 2-butene by distillation unless using a lot of
means. Thus, a significant amount of research related to a
separation process of isobutene and 1-butene has been conducted,
and a method of using isomerization of 1-butene and 2-butene has
been introduced as a typical example.
[0006] Hereinafter, a conventional processing method will be
described with reference to FIG. 1, wherein, as illustrated in FIG.
1, a conventional separation process has been performed by a
process system including an isomerization reactor R1, a
distillation column S1, a condenser C1, a reflux drum D1, a pump
P1, and a reboiler B1. For example, an olefin fraction including
isobutene, 1-butene, and 2-butene is supplied to the isomerization
reactor R1 through a reactant supply line F1 and is then supplied
to the distillation column S1 through a reaction product fraction
transfer line L1 after a portion of the 1-butene is converted into
2-butene. The supplied reaction product is separated in the
distillation column S1 so that a top fraction including isobutene
is transferred to the condenser C1 through an overhead discharge
line L2, condensed, and then introduced into the reflux drum D1
through reflux line 4 L3. A liquid in the top fraction in the
reflux drum D1 is reintroduced into the distillation column S1
through reflux line 5 L4, and a gas is discharged through a
recovery line L5. A bottom fraction including normal butene is
transferred to a recovery line L8 through a bottom discharge line
L6 and discharged, or is transferred to the reboiler B1, vaporized,
and then reintroduced into the distillation column S1 through
reflux line 6 L7. With respect to the conventional method as
described above, since the isomerization reactor must not only be
separately provided but also there is a need to use the condenser
and reboiler, a process may be somewhat cumbersome and economic
efficiency may not be good.
[0007] Thus, there is a need to develop a process which may easily
recover normal butene from a reaction mixture including isobutene,
isobutane, 1-butene, and 2-butene and may increase the economic
efficiency while having high separation and recovery
efficiency.
PRIOR ART DOCUMENT
[0008] (Patent Document 1) JP2000-0029848 A
DISCLOSURE OF THE INVENTION
Technical Problem
[0009] An aspect of the present invention provides a separation
method for easily recovering normal butene composed of 1-butene and
2-butene from an olefin fraction including isobutene, isobutane,
1-butene, 2-butene, and normal butane.
[0010] Another aspect of the present invention provides a
separation process system for easily recovering normal butene from
an olefin fraction.
Technical Solution
[0011] According to an aspect of the present invention, there is
provided a separation method for recovering normal butene from an
olefin fraction including the steps of: introducing an olefin
fraction into a distillation column including at least one
isomerization reaction zone (step 1); recovering a top fraction
including isobutene and isobutane from a top of the distillation
column and recovering a bottom fraction including normal butene
from a bottom of the distillation column (step 2); compressing at
least a portion of the top fraction to be heat-exchanged with at
least a portion of the bottom fraction (step 3); and reintroducing
at least a portion of the heat-exchanged top fraction and at least
a portion of the bottom fraction into the top and the bottom of the
distillation column, respectively (step 4).
[0012] According to another aspect of the present invention, there
is provided a separation process system for recovering normal
butene from an olefin fraction including: a supply unit which
supplies a reactant including an olefin fraction; a processing unit
connected to the supply unit, in which a distillation column
including at least one isomerization reaction zone is disposed; and
a recovery unit which is connected to the processing unit and
recovers a reaction product, wherein the distillation column of the
processing unit includes an overhead discharge line and a bottom
discharge line, and the recovery unit includes a top fraction
recovery unit connected to the overhead discharge line and a bottom
fraction recovery unit connected to the bottom discharge line.
Advantageous Effects
[0013] Since a separation method for separating normal butene from
an olefin fraction according to the present invention may easily
convert 1-butene included in the olefin fraction to 2-butene,
normal butene may be effectively separated and recovered by
factional distillation and each recovered fraction may be easily
refluxed even if the use of a reflux system using a refrigerant is
reduced or excluded. Thus, economic efficiency may be improved and
simultaneously, separation efficiency may be increased.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The following drawings attached to the specification
illustrate preferred examples of the present invention by example,
and serve to enable technical concepts of the present invention to
be further understood together with detailed description of the
invention given below, and therefore the present invention should
not be interpreted only with matters in such drawings.
[0015] FIG. 1 schematically illustrates a conventional process
system for separating normal butene from a typical olefin fraction;
and
[0016] FIG. 2 schematically illustrates a separation process system
for separating normal butene from an olefin fraction according to
an embodiment of the present invention.
MODE FOR CARRYING OUT THE INVENTION
[0017] Hereinafter, the present invention will be described in more
detail to allow for a clearer understanding of the present
invention.
[0018] It will be understood that words or terms used in the
specification and claims shall not be interpreted as the meaning
defined in commonly used dictionaries. It will be further
understood that the words or terms should be interpreted as having
a meaning that is consistent with their meaning in the context of
the relevant art and the technical idea of the invention, based on
the principle that an inventor may properly define the meaning of
the words or terms to best explain the invention.
[0019] The present invention provides a separation method for
recovering normal butene from an olefin fraction which may maximize
a recovery rate of the normal butene while reducing economic
costs.
[0020] In general, normal butene (1-butene and 2-butene) may be
used in the preparation of propylene or may be used in the
production of ethylene and hexene, and particularly, 1-butene is
used as a monomer for copolymerization of high density polyethylene
(HDPE) or linear low density polyethylene (LLDPE). The normal
butene may be recovered from a C4 residue or the like obtained from
a naphtha cracking process and used. However, since isobutene and
isobutane, in addition to the normal butene (1-butene and
2-butene), are included in the C4 residue or the like and boiling
points of the 1-butene (-6.24.degree. C.) and the isobutene
(-6.9.degree. C.) are very similar, it is almost impossible to
separate the 1-butene and the isobutene simply by fractional
distillation, a complicated process may be required to separate the
1-butene and the isobutene, and economic efficiency may not be
good. Thus, the 1-butene and the isobutene must be easily separated
in order to increase economic utilization of the normal butene
(1-butene and 2-butene). Thus, the present invention provides a
separation method for easily recovering normal butene from an
olefin fraction by converting 1-butene in the olefin fraction
including isobutene, isobutane, 1-butene, and 2-butene to 2-butene
using a distillation column, in which an isomerization reaction
zone is included, and simultaneously performing fractional
distillation.
[0021] The separation method according to an embodiment of the
present invention includes the steps of: introducing an olefin
fraction into a distillation column including at least one
isomerization reaction zone (step 1); recovering a top fraction
including isobutene and isobutane from a top of the distillation
column and recovering a bottom fraction including normal butene
from a bottom of the distillation column (step 2); compressing at
least a portion of the top fraction to be heat-exchanged with at
least a portion of the bottom fraction (step 3); and reintroducing
at least a portion of the heat-exchanged top fraction and at least
a portion of the bottom fraction into the top and the bottom of the
distillation column, respectively (step 4).
[0022] Herein, the separation method for recovering normal butene
may be a method of preparing normal butene, and, in this case, the
normal butene may partially include 1-butene, but 2-butene may be a
main component.
[0023] Step 1 is for facilitating the separation from isobutene by
converting 1-butene included in an olefin fraction into 2-butene
and performing fractional distillation, wherein it is a step of
introducing the olefin fraction into a distillation column
including an isomerization reaction zone.
[0024] The olefin fraction may include isobutene, isobutane,
1-butene, 2-butene, and normal butane. Specifically, the olefin
fraction may be a C4 residue obtained from naphtha cracking and may
be C4 residue I, in which butadiene is removed from the C4 residue,
C4 residue II, C4 residue 2.5, C4 residue III, or a combination
thereof. In this case, the olefin fraction may include less than 60
wt % of butadiene based on a total weight of the fraction, and an
amount of the 1-butene in the olefin fraction may be in a range of
1 wt % to 500 wt % based on the 2-butene.
[0025] The isomerization reaction zone may be a region in which at
least a portion of the 1-butene in the olefin fraction is converted
to 2-butene. Specifically, the isomerization reaction zone may be a
region in which selective positional isomerization occurs, and the
selective positional isomerization may denote isomerization in
which regioselective conversion of one isomer to another isomer
occurs. That is, the isomerization reaction zone according to the
present invention may be a region in which at least a portion of
1-butene is converted to 2-butene by the selective positional
isomerization.
[0026] The expression "at least a portion" used in the present
invention denotes a minimum of one or more portions, wherein at
least a portion of 1-butene, for example, may represent a portion
of the 1-butene, a portion or more of the 1-butene, or all of the
1-butene.
[0027] An isomerization catalyst may be included in the
isomerization reaction zone according to an embodiment of the
present invention, and the isomerization catalyst may be used
without limitation as long as it is known in the art, but the
isomerization catalyst, for example, may include at least one metal
selected from the group consisting of ruthenium (Ru), rhodium (Rh),
palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt), nickel
(Ni), tungsten (W), titanium (Ti), aluminum (Al), tantalum (Ta),
niobium (Nb), molybdenum (Mo), vanadium (V), rhenium (Re), and
gallium (Ga). The metal itself may be used as the catalyst, or the
catalyst may be used in a state of being attached to a separate
support. In a case in which the catalyst is used in a state of
being attached to the support, the support may include at least one
selected from the group consisting of silica-alumina, silica,
zeolite, activated carbon, clay, alumina-based cement, rare earth
metal oxide, and alkaline earth metal oxide.
[0028] A catalyst commercially available in the art may be
purchased and used as the catalyst, or the catalyst may be prepared
and used. Examples of the commercially available catalyst may be
E-144 SDU (BASF) and E-445 SDU (BASF).
[0029] In a case in which the catalyst is prepared and used, a
preparation method is not particularly limited, but the catalyst
may be prepared by a method known in the art.
[0030] The distillation column according to an embodiment of the
present invention includes an isomerization reaction zone in the
inside thereof and has both isomerization reaction zone and
distillation zone. That is, isomerization and fractional
distillation may simultaneously occur in the same physical space,
and the catalyst included in the isomerization reaction zone may
not only be in contact with the olefin fraction introduced before
the isomerization, but also may be in contact with at least a
portion of the top fraction reintroduced into the top of the column
and moving downward and may be in contact with at least a portion
of the bottom fraction reintroduced into the bottom of the
distillation column and moving upward. Thus, the isomerization
reaction zone may be located at a midpoint of the distillation
column for the smooth circulation of reactants (e.g., olefin
fraction and reintroduced top fraction and bottom fraction) in the
distillation column, and specifically, may be located at a position
higher than the midpoint based on a total height of the
distillation column. For example, the isomerization reaction zone
may be located in the top 5% to 50% based on the total height of
the distillation column.
[0031] Also, reaction conditions in the isomerization reaction zone
may be related to fractional distillation conditions of the
distillation zone. For example, pressures of the entire
distillation column are set to the same level and a different
temperature condition may be used for each zone. Specifically, the
distillation zone of the top of the column may have a temperature
of 0.degree. C. to 190.degree. C. under a pressure condition of
0.001 kgf/cm.sup.2 to 20 kgf/cm.sup.2, and the isomerization
reaction zone may have a temperature of 5.degree. C. to 200.degree.
C. under a pressure condition of 0.001 kgf/cm.sup.2 to 20
kgf/cm.sup.2.
[0032] In this case, when the temperature is less than 5.degree.
C., since the activity of the catalyst may be reduced, the
isomerization in the isomerization reaction zone may not occur
smoothly, and when the temperature is greater than 200.degree. C.,
1-butene may not be sufficiently converted due to an
equilibrium.
[0033] The separation method according to the embodiment of the
present invention may include introducing hydrogen into the
distillation column, if necessary, before the performance of the
isomerization in step 1. In this case, the separation method may
further include separating hydrogen from the recovered top
fraction, and the separated hydrogen may be reused.
[0034] Step 2 is a step for recovering a top fraction and a bottom
fraction which are separated by the distillation column including
the isomerization reaction zone.
[0035] The top fraction may include isobutene and isobutane, and
may be recovered from the top of the distillation column. In this
case, the top fraction may partially include unreacted 1-butene in
addition to the isobutene and the isobutane, and an amount of the
unreacted 1-butene included in the top fraction may be in a range
of 0% to 10% based on a total flow (kg/hr) of the top fraction. The
unreacted 1-butene may be reintroduced into the distillation column
through steps 3 and 4 to be described later.
[0036] The bottom fraction may include normal butene and may be
recovered from the bottom of the distillation column. The normal
butene may partially include 1-butene, and 2-butene may be a main
component. An amount of the 1-butene in the bottom fraction
recovered from the bottom may be in a range of 0% to 5% based on a
total flow (kg/hr) of the bottom fraction. In this case, the bottom
fraction may partially include isobutene and isobutane in addition
to the normal butene, and an amount of the isobutene and isobutane
included in the bottom fraction may be in a range of 0% to 5% based
on the total flow (kg/hr) of the bottom fraction.
[0037] Step 3 is a step of condensing at least a portion of the top
fraction and vaporizing at least a portion of the bottom fraction
in order to reintroduce at least a portion of each of the top
fraction and the bottom fraction recovered in step 2 into the
distillation column. Also, step 4 is a step of respectively
reintroducing the at least a portion of the condensed top fraction
and the at least a portion of the vaporized bottom fraction in step
3 into the top and the bottom of the distillation column to allow
them to again participate in the reaction.
[0038] As described above, the top fraction recovered from the top
may partially include unreacted 1-butene, and the bottom fraction
recovered from the bottom may partially include isobutene and
isobutane. Thus, there is a need to reduce an amount of the
consumed 1-butene by reintroducing the unreacted 1-butene included
in the top fraction, and there is a need to increase purity of the
normal butene in the bottom fraction by reducing an amount of the
isobutene and isobutane in the bottom fraction through the
reintroduction of the isobutene and isobutane included in the
bottom fraction.
[0039] Conventionally, in order to achieve the above-described
object, a method has been used in which a top fraction is
reintroduced into a distillation column by condensing the top
fraction recovered through a condenser using a refrigerant, and a
bottom fraction is reintroduced into the distillation column by
heating and vaporizing the bottom fraction recovered through a
reboiler (see FIG. 1). However, a large amount of the refrigerant
is necessary for the condensation, economic efficiency may be
reduced due to the high price of the refrigerant, and a high cost
is required in order for the reboiler to provide high heat.
[0040] In contrast, with respect to the method through step 3
according to the embodiment of the present invention, a process for
achieving the above-described object may be performed without using
separate condenser and reboiler, and thus, there is an effect of
reducing economic costs.
[0041] Step 3 may be performed by compressing at least a portion of
the recovered top fraction to be heat-exchanged with at least a
portion of the bottom fraction. That is, the heat exchange
according to an embodiment of the present invention may be
performed by a difference between a temperature of the at least a
portion of the top fraction and a temperature of the at least a
portion of the bottom fraction, and the at least a portion of the
top fraction and the at least a portion of the bottom fraction
before the heat exchange may have a temperature difference of
5.degree. C. to 200.degree. C.
[0042] Specifically, the at least a portion of the top fraction
before the heat exchange may have a temperature of 0.degree. C. to
400.degree. C. In this case, the at least a portion of the top
fraction before the heat exchange may be subjected to a compression
process in a compressor. Also, the at least a portion of the top
fraction may be subjected to a step of proving heat to prevent
condensation before the compression. In this case, the heat may be
provided by a typical method known in the art, and, for example, a
heat exchanger may be used.
[0043] Also, the at least a portion of the bottom fraction before
the heat exchange may have a temperature of 5.degree. C. to
200.degree. C.
[0044] The at least a portion of the top fraction may be condensed
by the heat exchange, and the at least a portion of the condensed
top fraction may be reintroduced into the top of the distillation
column as a reflux. In this case, a reintroduction rate (reflux
ratio) of the at least a portion of the top fraction reintroduced
into the top of the distillation column may be in a range of 50% to
99% based on the total flow (kg/hr) of the top fraction.
[0045] Furthermore, the at least a portion of the bottom fraction
may be heated and vaporized by the heat exchange, and the at least
a portion of the vaporized bottom fraction may be reintroduced into
the bottom of the distillation column as a reflux. In this case, a
reintroduction rate (reflux ratio) of the at least a portion of the
bottom fraction reintroduced into the bottom of the distillation
column may be in a range of 50% to 99% based on the total flow
(kg/hr) of the bottom fraction.
[0046] Since the separation method according to the embodiment of
the present invention may convert 1-butene to 2-butene by using the
distillation column including the isomerization reaction zone and
may simultaneously perform fractional distillation, isobutene and
1-butene may be easily separated without the use of a separate
isomerization reactor, and at least a portion of the top fraction
may be condensed and at least a portion of the bottom fraction may
be vaporized through the heat exchange using the difference between
the temperatures of the recovered top fraction and bottom fraction
to be reintroduced into the distillation column. Thus, the process
may be simplified and the economic efficiency may be improved.
[0047] 1-butene and 2-butene may be separated by separate
isomerization and fractional distillation of the recovered bottom
fraction. In this case, the isomerization and fractional
distillation may be performed by a typical method known in the
art.
[0048] For example, the recovered bottom fraction is introduced
into the distillation column including the isomerization reaction
zone to convert a portion of 2-butene in the bottom fraction to
1-butene, and fraction distillation is performed to recover
1-butene from the top and recover 2-butene from the bottom so that
the 1-butene and the 2-butene may be separated. In this case, the
isomerization reaction zone may include a catalyst capable of
regioselectively converting 2-butene to 1-butene.
[0049] Also, the present invention provides a separation process
system for recovering normal butene from an olefin fraction. The
separation process system may be used to perform a separation
process by the above-described separation method.
[0050] The separation process system according to an embodiment of
the present invention includes a supply unit which supplies a
reactant including an olefin fraction; a processing unit connected
to the supply unit, in which a distillation column including at
least one isomerization reaction zone is disposed; and a recovery
unit which is connected to the processing unit and recovers a
reaction product, wherein the distillation column of the processing
unit includes an overhead discharge line and a bottom discharge
line, and the recovery unit includes a top fraction recovery unit
connected to the overhead discharge line and a bottom fraction
recovery unit connected to the bottom discharge line.
[0051] Hereinafter, the separation process system according to the
embodiment of the present invention will be described with
reference to FIG. 2. In this case, since descriptions other than
equipment layout, design, and structure of the separation process
system overlap with those described in the above-described
separation method, the descriptions thereof will be omitted.
[0052] The supply unit is connected to the processing unit and may
include a supply line 10 which supplies a reactant including an
olefin fraction to the processing unit. The supply line may be
connected to a stream in which a C4 residue is recovered from
naphtha cracking. Also, the supply unit may further include a
storage tank if necessary, and the storage tank may be disposed in
the middle of the supply line and the stream, in which the C4
residue is recovered from the naphtha cracking, to control the flow
of the reactant supplied to the processing unit. The reactant
including an olefin fraction supplied through the supply line may
include isobutene, isobutane, 1-butene, 2-butene, and normal
butane. Specifically, the olefin fraction may be the same as
described above. For example, the olefin fraction may be a C4
residue obtained from naphtha cracking, and may be C4 residue I in
which butadiene is removed from the C4 residue, C4 residue II, C4
residue 2.5, C4 residue III, or a combination thereof.
[0053] Also, the supply unit may further include a hydrogen supply
line which supplies hydrogen to the processing unit.
[0054] The processing unit may include a distillation column 30
including an isomerization reaction zone 31, and the distillation
column 30 may be connected to the supply line 10 through which the
reactant is supplied. The supply line 10 may be connected to a
midpoint in a height direction of the distillation column 30 or may
be connected to a point at which the isomerization reaction zone 31
is included.
[0055] The isomerization reaction zone 31 may be a region in which
selective isomerization, which converts at least a portion of
1-butene in the reactant introduced through the supply line 10 to
2-butene, is performed, and an isomerization catalyst may be
included in the isomerization reaction zone 31. In this case, the
isomerization catalyst may be the same as described above.
[0056] The isomerization reaction zone is not particularly limited,
but the isomerization reaction zone may be located in the top 5% to
50% of the total height of the distillation column for smooth
isomerization. That is, the isomerization reaction zone 31 may be
disposed at a position higher than the midpoint in the height
direction of the distillation column 30.
[0057] Furthermore, the distillation column 30 of the processing
unit may include an overhead discharge line 11 for discharging a
top fraction separated by fractional distillation and a bottom
discharge line 20 for discharging a bottom fraction.
[0058] The recovery unit is connected to the processing unit to
recover a reaction product separated through the distillation
column 30 of the processing unit, wherein the recovery unit may
include a top fraction recovery unit connected to the overhead
discharge line 11 and a bottom fraction recovery unit connected to
the bottom discharge line 20, and the top fraction recovery unit
and the bottom fraction recovery unit may respectively include a
first reflux line and a second reflux line which are configured to
reintroduce at least a portion of each fraction into the processing
unit. Herein, the first reflux line, as a transfer line for
refluxing the top fraction, may include reflux line-1 12, reflux
line-2 13, reflux line-4 14, and reflux line-5 18 which will be
described later, and the second reflux line, as a transfer line for
refluxing the bottom fraction, may include reflux line-3 21 and
reflux line-6 22 which will be described later.
[0059] Specifically, a compressor 33, a heat exchanger 36, and a
reflux drum 34 may be disposed in the recovery unit, and the
recovery unit may be connected to the compressor 33, the heat
exchanger 36, and the reflux drum 34 to include a plurality of
lines that transfer the top fraction or the bottom fraction.
[0060] The top fraction recovery unit may include a top fraction
recovery line 19, which recovers the top fraction transferred from
the overhead discharge line 11, and the plurality of reflux lines
for reintroducing at least a portion of the fraction into the
processing unit. The overhead discharge line 11 may be connected to
the reflux drum 34 of the top fraction recovery unit, and the top
fraction may be transferred into the reflux drum 34 through the
overhead discharge line 11. Also, the at least a portion of the top
fraction may be transferred to the compressor 33 through the reflux
line-1 12 which is connected to the overhead discharge line 11. In
this case, the top fraction transferred through the overhead
discharge line 11 may be heated by the heat exchanger and may then
be transferred to the reflux drum 34 or the compressor 33.
Furthermore, the reflux drum 34 may be connected to the reflux
line-4 14, and at least a portion of the top fraction condensed
through the reflux line-4 14 may be transferred to the reflux drum
34. The at least a portion of the top fraction transferred to the
compressor 33 may be compressed and transferred to the heat
exchanger 36 through the reflux line-2 13 which is connected to the
heat exchanger 36.
[0061] Also, the bottom fraction recovery unit may include a bottom
fraction recovery line 23, which recovers the bottom fraction
transferred from the bottom discharge line 20, and the plurality of
reflux lines for reintroducing at least a portion of the bottom
fraction into the processing unit. The bottom fraction may be
discharged to the bottom fraction recovery line 23 through the
bottom discharge line 20 and recovered, and the at least a portion
of the bottom fraction may be transferred to the heat exchanger
through the reflux line 3 21 which is connected to the heat
exchanger 36.
[0062] The heat exchanger 36 may be operated by the heat exchange
between the at least a portion of the top fraction transferred
through the reflux line-2 13 and the at least a portion of the
bottom fraction transferred through the reflux line-3 21, and thus,
the at least a portion of the top fraction may be condensed and the
at least a portion of the bottom fraction may be vaporized.
[0063] The at least a portion of the condensed top fraction may be
transferred to the reflux drum 34 through the reflux line-4 14 as
described above. The gas-phase top fraction transferred from the
overhead discharge line 11 and at least a portion of the
liquid-phase top fraction transferred through the reflux line-4 14
are included in the reflux drum 34, and the liquid phase and gas
phase are separated through the reflux drum 34 so that the at least
a portion of the liquid-phase top fraction is reintroduced into the
processing unit through the reflux line-5 18, and the gas-phase top
fraction may be discharged through the top fraction recovery line
19 and recovered.
[0064] Also, at least a portion of the vaporized bottom fraction
may be reintroduced into the processing unit through the reflux
line-6 22.
[0065] As described above, since the separation process system
according to the embodiment of the present invention isomerizes
1-butene into 2-butene through the processing unit in which the
distillation column including the isomerization reaction zone is
disposed, 1-butene and isobutene may not only be easily separated,
but each fraction may also be effectively refluxed into the
processing unit without the use of a separate reflux system (e.g.,
condenser and reboiler). Thus, process efficiency may be improved
and simultaneously, economic costs may be reduced.
[0066] Hereinafter, the present invention will be described in more
detail, according to the following examples. However, the following
examples are merely presented to exemplify the present invention,
and the scope of the present invention is not limited thereto.
[0067] In the following example and comparative example, the
separation method according to the present invention was simulated
by using ASPEN PLUS, a commercial process simulation program.
Program's built-in values, values described in the literature, and
values obtained from conventional C4 separation and manufacturing
processes were used as constants required for the simulation.
EXAMPLE
[0068] In a distillation column including an isomerization reaction
zone, a number of theoretical plates was set to 100, the
isomerization reaction zone was set between the 20.sup.th plate and
the 40.sup.th plate, a top pressure was fixed to 4 kgf/cm.sup.2G, a
temperature of the top of the distillation column was adjusted to
39.degree. C., and a temperature of the isomerization reaction zone
was adjusted to be in a range of 46.degree. C. to 51.degree. C. A
selectivity of a catalyst included in the isomerization reaction
zone was assumed to be 100%. An olefin fraction, as a reactant, was
set to have a composition including 0.5 wt % of propylene, 25.0 wt
% of isobutane, 20.0 wt % of isobutene, 15.0 wt % of 1-butene, 31.0
wt % of 2-butene, 8.0 wt % of normal butane, and 0.5 wt % of normal
pentane, and a total flow was set to 10,000 kg/hr. Reflux ratios of
refluxed top fraction and bottom fraction were respectively
adjusted to be 96.37% and 95.76%, and results of process
performance are presented in the following Table 1. In this case,
heat duty was 0 Gcal/hr and cooling duty was -1.14 Gcal/hr.
TABLE-US-00001 TABLE 1 Recovered Recovered top bottom Reactant
fraction fraction Category (wt %) (wt %) (wt %) Propylene 0.5 1.09
0.0 Isobutane 25.0 54.32 0.0 Isobutene 20.0 43.27 0.16 1-butene
15.0 0.3 0.08 Normal butane 8.0 0.83 14.11 2-butene 31.0 0.19 84.73
Normal pentane 0.5 0.0 0.93 Total flow (kg/hr) 10,000 4.602
5.398
Comparative Example
[0069] A process was performed by using the same conditions as
those of the example except that a simulation was performed by a
process system as illustrated in FIG. 2 and conditions of an
isomerization reactor was separately set. In this case, the
isomerization reactor was set to a temperature of 50.degree. C. and
a pressure of 4.8 kgf/cm.sup.2G. Results were presented in the
following Table 2, heat duty was 10.06 Gcal/hr, and cooling duty
was -10.01 Gcal/hr.
TABLE-US-00002 TABLE 2 Fraction discharged Recovered Recovered from
top bottom Reactant reactor fraction fraction Category (wt %) (wt
%) (wt %) (wt %) Propylene 0.5 0.5 1.09 0.0 Isobutane 25.0 25.0
54.34 0.01 Isobutene 20.0 20.0 40.84 2.25 1-butene 15.0 1.8 3.74
0.14 Normal butane 8.0 8.0 0.0 14.81 2-butene 31.0 44.20 0.0 81.83
Normal pentane 0.5 0.5 0.0 0.93 Total flow 10,000 10,000 4,600
5,400 (kg/hr)
[0070] As illustrated in Tables 1 and 2, with respect to the
separation process of the example according to an embodiment of the
present invention, a composition ratio of unreacted 1-butene in the
recovered top fraction was 0.3 wt %, but, with respect to the
separation process of the comparative example, a composition ratio
of unreacted 1-butene in the recovered top fraction was 3.74 wt %.
Also, with respect to the separation process according to the
example, a composition ratio of isobutene in the recovered bottom
fraction was 0.16 wt %, but, with respect to the separation process
of the comparative example, a composition ratio of isobutene in the
recovered bottom fraction was 2.25 wt %. That is, the amount of the
unreacted 1-butene in the top fraction separated by the separation
process according to the example was decreased by about 1/12 in
comparison to the separation process of the comparative example,
and the amount of the isobutene in the bottom fraction was
decreased by about 1/13 in comparison to the separation process of
the comparative example.
[0071] Furthermore, with respect to the separation process of the
example according to the embodiment of the present invention, since
the top fraction was condensed and refluxed and the bottom fraction
was vaporized and refluxed by the heat exchange between the two
fractions using a temperature difference between the top fraction
and the bottom fraction without the use of a separate reflux system
(condenser and reboiler) for refluxing each of the top fraction and
the bottom fraction, heat duty was reduced by 100% and cooling duty
was reduced by about 88% in comparison to the separation process of
the comparative example using a separate reflux system.
[0072] As confirmed by the above results, with respect to the
separation process of the example according to the embodiment of
the present invention, since 1-butene was converted to 2-butene by
using the distillation column including the isomerization reaction
zone and simultaneously, fractional distillation was performed,
isobutene and 1-butene may be easily separated by a simplified
process. In addition, since a separate reflux system was not used,
an effect of reducing costs may be obtained. Also, as can be seen
from the composition ratios of the top fraction and the bottom
fraction, the separation process according to the embodiment of the
present invention may easily reflux each of the top fraction and
the bottom fraction without the use of a separate reflux
system.
[0073] Thus, since the separation method and separation process
system for recovering normal butene from an olefin fraction
according to the present invention may effectively separate
isobutene and 1-butene from the olefin fraction including
isobutene, isobutane, 1-butene, and 2-butene by a simplified
process, high-purity normal butene may be recovered.
Simultaneously, since each of the recovered top fraction and bottom
fraction may be refluxed without the separate use of condenser and
reboiler, separation efficiency may be further increased while
reducing costs.
* * * * *