U.S. patent application number 16/022491 was filed with the patent office on 2020-01-02 for membrane process for olefin separation.
The applicant listed for this patent is UOP LLC. Invention is credited to Stanley J. Frey, J. Mark Houdek, Chunqing Liu, Trung Pham.
Application Number | 20200001242 16/022491 |
Document ID | / |
Family ID | 68841451 |
Filed Date | 2020-01-02 |
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United States Patent
Application |
20200001242 |
Kind Code |
A1 |
Frey; Stanley J. ; et
al. |
January 2, 2020 |
MEMBRANE PROCESS FOR OLEFIN SEPARATION
Abstract
A process is provided to separate a hydrocarbon stream
comprising a mixture of light olefins and light paraffins, the
process comprising sending the hydrocarbon stream through a
pretreatment unit to remove impurities selected from the group
consisting of sulfur compounds, arsine, phosphine, methyl
acetylene, propadiene, and acetylene to produce a treated
hydrocarbon stream; vaporizing the treated hydrocarbon stream to
produce a gaseous treated hydrocarbon stream; adding liquid or
vapor water to the gaseous treated hydrocarbon stream; then
contacting the gaseous treated hydrocarbon stream to a membrane in
a membrane system comprising one or more membrane units to produce
a permeate stream comprising about 96 to 99.9 wt % light olefins
and a retentate stream comprising light paraffins.
Inventors: |
Frey; Stanley J.; (Palatine,
IL) ; Houdek; J. Mark; (Bartlett, IL) ; Liu;
Chunqing; (Arlington Heights, IL) ; Pham; Trung;
(Mount Prospect, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UOP LLC |
Des Plaines |
IL |
US |
|
|
Family ID: |
68841451 |
Appl. No.: |
16/022491 |
Filed: |
June 28, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C07C 5/09 20130101; B01D
53/228 20130101; B01D 2311/10 20130101; B01D 67/0088 20130101; B01D
2257/702 20130101; C07C 2523/44 20130101; B01D 67/0079 20130101;
B01D 69/142 20130101; C07C 2523/755 20130101; C07C 7/12 20130101;
B01D 71/76 20130101; B01D 2311/04 20130101; C10G 2400/20 20130101;
C07C 7/144 20130101; B01D 53/226 20130101; B01D 2325/10 20130101;
C07C 2523/42 20130101; B01D 2311/14 20130101; C07C 7/12 20130101;
C07C 11/04 20130101; C07C 7/12 20130101; C07C 11/06 20130101; C07C
5/09 20130101; C07C 11/04 20130101; C07C 5/09 20130101; C07C 11/06
20130101; C07C 7/144 20130101; C07C 11/04 20130101; C07C 7/144
20130101; C07C 11/06 20130101 |
International
Class: |
B01D 67/00 20060101
B01D067/00; B01D 69/14 20060101 B01D069/14; B01D 71/76 20060101
B01D071/76; C07C 7/144 20060101 C07C007/144 |
Claims
1. A process to separate a liquid hydrocarbon stream comprising a
mixture of light olefins and light paraffins, said process
comprising: sending said hydrocarbon stream through a pretreatment
unit to remove impurities selected from the group consisting of
sulfur compounds, arsine and phosphine and then through a selective
hydrogenation unit to selectively hydrogenate methyl acetylene and
acetylene to produce a treated liquid hydrocarbon stream; adding
liquid or vapor water to said treated liquid hydrocarbon stream;
vaporizing said treated liquid hydrocarbon stream to produce a
gaseous treated hydrocarbon stream; and then contacting said
gaseous treated hydrocarbon stream to a membrane in a membrane
system comprising one or more membrane units to produce a permeate
stream comprising about 96 to 99.9 wt % light olefins and a
retentate stream comprising light paraffins.
2-3. (canceled)
4. The process of claim 1 wherein said selective hydrogenation unit
removes hydrogen to reduce a level of hydrogen in said treated
liquid hydrocarbon stream to about 5 ppm or less.
5. The process of claim 1 wherein said selective hydrogenation unit
contains a catalyst selected from the group consisting of reduced
forms of Pt, Pd and Ni catalysts.
6. The process of claim 1 wherein said hydrocarbon stream comprises
less than about 80 wt % light olefins.
7. The process of claim 1 wherein said light olefins comprise
ethylene or propylene.
8. The process of claim 1 wherein sufficient liquid or water vapor
is added to said gaseous treated hydrocarbon so that said gaseous
treated hydrocarbon stream has from 50 to 90% humidity when
contacting said membrane.
9. The process of claim 1 wherein said membrane system comprises a
single stage membrane.
10. The process of claim 1 wherein said membrane system comprises a
two stage membrane system wherein a retentate from a first membrane
unit is contacted to a second membrane unit to produce a second
permeate stream and a second retentate stream.
11. The process of claim 10 wherein said second permeate stream is
recycled to said gaseous treated hydrocarbon stream.
12. The process of claim 1 wherein said membrane system comprises a
three stage membrane system wherein a retentate from a first
membrane unit is contacted to a second membrane unit to produce a
second permeate stream and a second retentate stream and said
second retentate stream is sent to a third membrane unit to produce
a third permeate stream and a third retentate.
13. The process of claim 12 wherein said third permeate is combined
with said second permeate and recycled to said gaseous treated
hydrocarbon stream.
14. The process of claim 1 wherein said membrane system is operated
at a temperature from about 30 to 80.degree. C.
15. The process of claim 1 wherein said gaseous treated hydrocarbon
stream is at a pressure from about 80 to about 300 psig before
entering a membrane unit.
16. The process of claim 1 wherein a concentration of light olefin
in the retentate stream from a single stage membrane system is
about 40-45 wt %.
17. The process of claim 1 wherein a membrane used in said membrane
system has a light olefin permeance of about 33-245 GPU and a light
olefin/light paraffin selectivity in a range of about 80-1000.
18. The process of claim 1 wherein said permeate stream comprises
about 99 to 99.5 wt % light olefins.
19. The process of claim 1 wherein said retentate comprises about
7-10 wt % light olefins.
20. (canceled)
Description
FIELD OF THE INVENTION
[0001] This invention relates to a process for upgrading a low
purity olefin/paraffin stream. More specifically, the invention
relates to a process for upgrading a low olefin purity
olefin/paraffin stream with less than about 80 wt % of olefin
coming from an olefin/paraffin splitter with a mixture of olefins
and a mixture of paraffins to higher olefin purity using a
standalone membrane system without interaction with an existing
column or any other column.
BACKGROUND OF THE INVENTION
[0002] Olefin producers usually sell or ship the low olefin purity
olefin/paraffin stream at a lower value (refinery grade). Upgrading
this stream on-site will bring much higher value due to higher
purity, chemical grade or polymer grade olefin. The process
disclosed in the current invention offers a process to upgrade low
olefin purity olefin/paraffin stream at the customer site to a
higher value stream, such as polymer grade propylene at high
recovery. The process disclosed in the present invention also
allows the installation of the membrane unit with a faster time
(modular built) than a conventional distillation column, which
takes longer to install, more costly and also takes up more
footprint.
[0003] Separation of light olefins from paraffins is an energy
intensive process. The current process involves traditional use of
distillation columns which include 100-200 equilibrium trays which
make these columns among the tallest in a refinery or petrochemical
complex.
[0004] Over 170 Separex.TM. membrane systems have been installed in
the world for gas separation applications such as for the removal
of acid gases from natural gas, in enhanced oil recovery, and
hydrogen purification. Two new Separex.TM. membranes (Flux+ and
Select) have been commercialized recently by Honeywell UOP, Des
Plaines, Ill. for carbon dioxide removal from natural gas. These
Separex.TM. spiral wound membrane systems currently hold the
membrane market leadership for natural gas upgrading. These
membranes, however, do not have outstanding performance for
olefin/paraffin separations. Development of new stable and very
high selectivity membranes is critical for the future success of
membranes for olefin/paraffin separation applications such as
propylene/propane and ethylene/ethane separations.
[0005] Light olefins, such as propylene and ethylene, are produced
as co-products from a variety of feedstocks in a number of
different processes in the chemical, petrochemical, and petroleum
refining industries. Various petrochemical streams contain olefins
and other saturated hydrocarbons. Typically, these streams are from
stream cracking units (ethylene production), catalytic cracking
units (motor gasoline production), or the dehydrogenation of
paraffins.
[0006] Currently, the separation of olefin and paraffin components
is performed by superfractionation with very high reflux ratios,
which is expensive and energy intensive due to the low relative
volatilities of the components. Large capital expense and energy
costs have created incentives for extensive research in this area
of separations, and low energy-intensive membrane separations have
been considered as an attractive alternative.
[0007] In principle, membrane-based technologies have the
advantages of both low capital cost and high-energy efficiency
compared to conventional separation methods for olefin/paraffin
separations, such as propylene/propane and ethylene/ethane
separations. Four main types of membranes have been reported for
olefin/paraffin separations. These are facilitated transport
membranes, polymer membranes, mixed matrix membranes, and inorganic
membranes. Facilitated transport membranes, or ion exchange
membranes, which sometimes use silver ions as a complexing agent,
have very high olefin/paraffin separation selectivity. However,
poor chemical stability, due to carrier poisoning or loss, high
cost, and low flux, currently limit practical applications of
facilitated transport membranes.
[0008] Separation of olefins from paraffins via conventional
polymer membranes has not been commercially successful due to
inadequate selectivities and permeabilities of the polymer membrane
materials, as well as due to plasticization and contamination
issues. Polymers that are more permeable are generally less
selective than are less permeable polymers. A general trade-off has
existed between permeability and selectivity (the so-called
"polymer upper bound limit") for all kinds of separations,
including olefin/paraffin separations. In recent years, substantial
research effort has been directed to overcoming the limits imposed
by this upper bound. Various polymers and techniques have been
used, but without much success in terms of improving the membrane
selectivity.
[0009] More efforts have been undertaken to develop metal ion
incorporated, high olefin/paraffin selectivity facilitated
transport membranes. The high selectivity for olefin/paraffin
separations is achieved by the incorporation of metal ions such as
silver (I) or copper (I) cations into the solid nonporous polymer
matrix layer on top of the highly porous membrane support layer
(so-called "fixed site carrier facilitated transport membrane") or
directly into the pores of the highly porous support membrane
(so-called "supported liquid facilitated transport membrane") that
results in the formation of a reversible metal cation complex with
the pi bond of olefins, whereas no interaction occurs between the
metal cations and the paraffins. Addition of water, plasticizer, or
humidification of the olefin/paraffin feed streams to either the
fixed site carrier facilitated transport membranes or the supported
liquid facilitated transport membranes is usually required to
obtain reasonable olefin permeances and high olefin/paraffin
selectivities. The performance of fixed site carrier facilitated
transport membranes is much more stable than that of the supported
liquid facilitated transport membranes and the fixed site carrier
facilitated transport membranes are less sensitive to the loss of
metal cation carriers than the supported liquid facilitated
transport membranes.
SUMMARY OF THE INVENTION
[0010] The invention involves a process to separate a hydrocarbon
stream comprising a mixture of light olefins and light paraffins,
particularly a process for upgrading an olefin/paraffin stream
coming from an olefin/paraffin splitter with a mixture of olefins
and a mixture of paraffins to higher olefin purity using a
standalone membrane system without interaction with an existing
column or any other column. The hydrocarbon stream that is sent to
the standalone membrane system comprises a feed from a refinery
grade propylene comprising less than about 80% of propylene. The
impurities that need to be removed from the hydrocarbon stream
before being treated by the membrane system of the present
invention comprise arsine, phosphine, sulfur compounds, hydrogen,
dienes and acetylenes. The first step of the process is to pretreat
the hydrocarbon stream using a pretreatment unit which includes an
adsorbent system followed by a selective hydrogenation unit to
remove impurities to produce a treated hydrocarbon stream. The
adsorbent system includes adsorbents such as those sold by UOP LLC
to remove sulfur (COS, mercaptan, hydrogen sulfide), arsine,
phosphine. While the adsorbents for sulfur and water removal are
typically regenerable and installed in swing vessels, the
adsorbents for arsine and phosphine are non-regenerable and
installed in a guard bed. The selective hydrogenation unit include
UOP commercial K-type of liquid process (KLP) or Pd type noble
metal catalysts to selectively hydrogenate methyl acetylene and
propadiene (MA/PD) to propylene since these compounds can permeate
through the membrane with propylene product and also contaminate
the membranes. The selective hydrogenation unit may include a
second layer of a selective hydrogenation reduced metal platinum,
palladium or nickel catalyst to actively consume extra hydrogen,
which is another contaminant for the membrane in the reactor down
to 0-10 ppm level, or preferably 0-5 ppm.
[0011] Then the treated hydrocarbon stream is vaporized to produce
a gaseous treated hydrocarbon stream and add liquid or vapor water.
The gaseous treated hydrocarbon stream is sent to a membrane
system. The treated stream pressure at the membrane inlet is about
80-300 psig, preferably about 100-240 psig, and the membrane
operation temperature is controlled at about 30-80.degree. C.,
preferably about 45-65.degree. C., with a humidity level at
40-100%, preferably 50-90%.
[0012] The membrane system described in the present invention can
be a single stage membrane system comprising a single stage
membrane unit, a two-stage membrane system comprising a first stage
and a second stage membrane units, or a three or more-stage
membrane system comprising a first stage, a second stage, a third
stage or even more stage membrane units. To produce a single grade,
high purity olefin such as polymer grade propylene (PGP, with about
99.5 wt % purity or higher), the second stage membrane permeate,
the second and third stage membrane permeates, or the second, third
and more stage membrane permeates can be recycled to the first
stage feed. The same membrane is used for the single stage membrane
system, the two-stage membrane system, or the three or more-stage
membrane system. The olefin permeance of the membrane used for the
membrane system in the present invention is about 33-245 GPU (1
GPU=10.sup.-6 cm.sup.3 (STP)/cm.sup.2seccmHg), preferably about
66-195 GPU and the olefin/paraffin selectivity of the membrane is
in the range of about 80-1000, preferably in the range of about
100-800.
[0013] The standalone membrane system described in the present
invention may comprise membrane units comprising membranes as
recently described in US 2018/0001277 A1; US 2018/0001268 A1; and
U.S. application Ser. No. 15/599,258 filed May 18, 2017
incorporated herein in their entireties.
[0014] The product stream from the permeate stream of the single
stage membrane system may comprise 99.5 to 99.9% propylene. The
hydrocarbon stream that is treated in the single stage membrane
system may be a refinery grade propylene with about 70 wt % of
propylene.
[0015] Sufficient water vapor is added to each hydrocarbon stream
before each stream contacts a membrane unit so that the stream has
from 40 to 100% humidity and more typically has from 50-90%
humidity. Accordingly, water vapor is added to the feed streams for
said single stage membrane unit in said single stage membrane
system, said first stage membrane unit and second stage membrane
unit in said two-stage membrane system, and said first stage
membrane unit, second stage membrane unit, third stage and more
stage membrane units in said three or more-stage membrane system
before each of said feed streams enters the membrane unit. The
membranes used in the first stage membrane unit, the second stage
membrane unit, the third stage membrane unit, and the even more
stage membrane unit are the same membranes that can be selected
from the membranes as recently described in US 2017/0354918 A1; and
U.S. application Ser. No. 15/615,134 filed Jun. 6, 2017.
incorporated herein in their entireties.
[0016] The hydrocarbon stream is at a pressure from about 80 to
about 300 psig, preferably from about 100 to about 240 psig, before
entering a membrane unit and is at a temperature from about 30 to
about 80.degree. C., preferably from about 45 to about 65.degree.
C. The main light olefins that are produced by the present
invention are ethylene and propylene. The process that is described
herein includes details for the production of propylene, but a
similar process may take place to produce ethylene.
[0017] Additional features and advantages of the invention will be
apparent from the description of the invention, figures and claims
provided herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a single stage membrane system to produce a
polymer grade propylene stream.
[0019] FIG. 2 is a two-stage membrane system to upgrade propylene
stream.
[0020] FIG. 3 is a three-stage membrane system to upgrade propylene
stream.
[0021] FIG. 4 is a two-stage membrane system to produce a single
polymer grade propylene stream.
[0022] FIG. 5 is a three-stage membrane system to produce a single
polymer grade propylene stream.
DETAILED DESCRIPTION OF THE INVENTION
[0023] The invention relates to a process for upgrading a low
olefin purity olefin/paraffin stream with less than about 80 wt %
of olefin coming from an olefin/paraffin splitter with a mixture of
olefins and a mixture of paraffins to higher olefin purity using a
standalone membrane system without interaction with an existing
column or any other column. The overall process includes a
pretreatment system followed by membrane separation system. The
pretreatment system includes adsorption units to remove impurities
such as arsine, phosphine, sulfur compounds including mercaptans
and other impurities present in the feed as well as a customized
catalyst system that can selectively hydrogenate methylacetylene,
acetylene, and propadiene contaminants to mono-olefins. While the
adsorbents for sulfur removal are typically regenerable and
installed in swing vessels, the adsorbents for arsine and phosphine
are non-regenerable and installed in a guard bed. The selective
hydrogenation unit include UOP commercial K-type of liquid process
(KLP) or noble metal palladium catalyst to selectively hydrogenate
methylacetylene, acetylene, and propadiene to ethylene and
propylene since these compounds can permeate through the membrane
with propylene product and also contaminate the membranes. The
selective hydrogenation unit may include a second layer of a
selective hydrogenation palladium catalyst such as reduced forms of
Pt, Pd or Ni, for example, if the K-type catalyst is used in the
first layer to actively consume extra H.sub.2, which is another
contaminant for the membrane in the reactor down to 0-10 ppm level,
or preferably 0-5 ppm. The treated liquid hydrocarbon feed is then
vaporized and heated to about 30-80.degree. C., preferably
45-65.degree. C. and added with water to 40-100% humidity,
preferably 50-90% humidity before entering the membrane system. The
treated hydrocarbon stream pressure at the membrane inlet is about
80 to about 300 psig, preferably about 100 to about 240 psig.
[0024] In one embodiment as shown in FIG. 1, a typical treated
hydrocarbon feed such as a low purity refinery grade propylene
comprising about 70 wt % propylene enters a single stage membrane
system to produce a high purity propylene permeate product with
99.5 wt % of propylene and approximately 70% propylene recovery
(propylene recovery is defined as the amount of propylene in the
permeate divided by the amount of propylene in the feed). The
concentration of propylene in the retentate from the single stage
membrane system is in the range of 40-45 wt %. The propylene
permeance of the membrane used for the single stage membrane system
in the present invention is about 33-245 GPU, preferably about
66-195 GPU and the propylene/propane selectivity is in the range of
about 80-1000, preferably in the range of about 100-800.
[0025] In FIG. 1, a feed 5 as described above is sent to a
pretreatment zone 10 to provide a treated stream 11 that is heated
by heater 20 and enters membrane unit 22 to be separated into a
permeate 25 and a residue 30. Water vapor is added at 15.
[0026] In a second embodiment of the invention as shown in FIG. 2,
a typical treated hydrocarbon feed such as a low purity refinery
grade propylene comprising about 70 wt % propylene is vaporized and
heated to about 30-80.degree. C., preferably 45-65.degree. C. and
added with water to 40-100% humidity, preferably 50-90% humidity
before entering a two-stage membrane system. The treated
hydrocarbon stream pressure at the membrane inlets for both the
first stage membrane unit and the second stage membrane unit is
about 80 to about 300 psig, preferably about 100 to about 240 psig.
The treated hydrocarbon stream enters a two-stage membrane system
to produce high purity propylene permeate products with about 98 wt
% to 99.5 wt % of propylene and improved propylene recovery to
about 92.5% compared to the single stage membrane system as shown
in FIG. 1. In the two-stage membrane system, about 69% of propylene
recovery goes to the premium propylene product at 99.5 wt % purity
in the permeate stream of the first stage membrane and an
additional about 23.5% propylene recovery goes to a propylene
product at about 98.4 wt % purity in the permeate stream of the
second stage membrane. The concentration of propylene in the
retentate of the first stage membrane is in the range of about
40-45 wt % and the concentration of propylene in the retentate of
the second stage membrane is about 35 wt %. The retentate of the
first stage membrane is humidified to 40-100% humidity, preferably
50-90% humidity and heated to about 30-80.degree. C., preferably
45-65.degree. C. before entering to the second stage membrane unit.
The membrane used in the first stage membrane unit and that used in
the second stage membrane unit in the two-stage membrane system
described in the present invention are the same membrane with
propylene permeance of about 33-245 GPU, preferably about 66-195
GPU and high propylene/propane selectivity in the range of about
80-1000, preferably in the range of about 100-800.
[0027] In FIG. 2, a feed 5 as described above is sent to a
pretreatment zone 10 to provide a treated stream 11 that is heated
by heater 20 and enters membrane unit 22 to be separated into a
permeate stream 25 and a retentate 30. Water vapor is added at 15
and 24. Retentate 30 is heated by heater 26 and passes through a
second membrane unit 28 to be separated into second permeate stream
35 and second retentate 40.
[0028] In a third embodiment of the invention as shown in FIG. 3, a
typical treated hydrocarbon feed such as a low purity refinery
grade propylene comprising about 70 wt % propylene is vaporized and
heated to about 30-80.degree. C., preferably 45-65.degree. C. and
added with water to 40-100% humidity, preferably 50-90% humidity
before entering a three-stage membrane system. The treated
hydrocarbon stream pressure at the membrane inlets for the first
stage membrane unit, the second stage membrane unit, and the third
stage membrane unit is about 80 to about 300 psig, preferably about
100 to about 240 psig. The treated hydrocarbon stream enters a
three-stage membrane system to produce high purity propylene
permeate products with about 96 wt % to 99.5 wt % of propylene and
improved overall propylene recovery to about 96.4% compared to the
single stage membrane system as shown in FIG. 1 and the two-stage
membrane system as shown in FIG. 2. In the three-stage membrane
system, about 69% of propylene recovery goes to the premium
propylene product at 99.5 wt % purity in the permeate stream of the
first stage membrane, about 23.5% of propylene recovery goes to a
propylene product at about 98.4 wt % purity in the permeate stream
of the second stage membrane, and about 3.9% of propylene recovery
goes to a propylene product at about 90.7 wt % purity in the
permeate stream of the third stage membrane. The secondary and
tertiary propylene product can be combined to produce a 96.9 wt %
purity propylene product. In some cases, additional stages can be
added to the multi-stage membrane system process to further improve
the propylene recovery. The concentration of propylene in the
retentate of the first stage membrane is in the range of about
40-45 wt %, the concentration of propylene in the retentate of the
second stage membrane is about 35 wt % and the concentration of
propylene in the retentate of the third stage membrane is about 8.6
wt %. The retentates of the first stage membrane unit and the
second stage membrane unit are humidified to 40-100% humidity,
preferably 50-90% humidity and heated to about 30-80.degree. C.,
preferably 45-65.degree. C. before entering to the second stage
membrane unit and the third stage membrane unit, respectively. The
membrane used in the first stage membrane unit, that used in the
second stage membrane unit, and that used in the third stage
membrane unit in the three-stage membrane system described in the
present invention are the same membrane with propylene permeance of
about 33-245 GPU, preferably about 66-195 GPU and high
propylene/propane selectivity in the range of about 80-1000,
preferably in the range of about 100-800.
[0029] In FIG. 3, a feed 5 as described above is sent to a
pretreatment zone 10 to provide a treated stream 11 that is heated
by heater 20 and enters membrane unit 22 to be separated into a
permeate stream 25 and a retentate 30. Water vapor is added at 15,
24 and 50. Retentate 30 is heated by heater 26 to produce a heated
retentate 42 that passes through a second membrane unit 44 to be
separated into second permeate stream 46 and second retentate 48.
Second permeate stream is mixed with a third permeate stream 56 to
become combined permeate stream 62. Retentate 48 is sent through
heater 52 to pass through a third membrane unit 54 to be separated
into permeate stream 56 and third retentate 58.
[0030] In a fourth embodiment of the invention as shown in FIG. 4,
a typical treated hydrocarbon feed such as a low purity refinery
grade propylene comprising about 70 wt % propylene is vaporized and
heated to about 30-80.degree. C., preferably 45-65.degree. C. and
added with water to 40-100% humidity, preferably 50-90% humidity
before entering a two-stage membrane system from which the permeate
of the second stage membrane unit is recycled to the membrane inlet
of the first stage membrane unit to provide a single polymer grade
propylene (PGP with propylene purity of 99.5 wt % or higher)
product. The treated hydrocarbon stream pressure at the membrane
inlets for both the first stage membrane unit and the second stage
membrane unit is about 80 to about 300 psig, preferably about 100
to about 240 psig. The treated hydrocarbon stream enters a
two-stage membrane system to produce a high purity single PGP
product with propylene purity of 99.5 wt % or higher in the
permeate of the first stage membrane unit and the permeate of the
second stage membrane is recycled back to the membrane inlet of the
first stage membrane unit. For example, the second stage permeate
with about 98 wt % propylene purity is recompressed, cooled and
controlled at about 30-80.degree. C., preferably at about
45-65.degree. C., and combined with the treated hydrocarbon feed to
the first stage membrane unit. The permeate of the first stage
membrane unit provides the high purity product with about 99.7 wt %
propylene and the total propylene recovery is about 91.6%. In the
two-stage membrane system with the permeate of the second stage
membrane unit recycled back to the feed of the first stage membrane
unit, the concentration of propylene in the retentate of the first
stage membrane is in the range of about 40-45 wt % and the
concentration of propylene in the retentate of the second stage
membrane is about 16 wt %. The retentate of the first stage
membrane is humidified to 40-100% humidity, preferably 50-90%
humidity and heated to about 30-80.degree. C., preferably
45-65.degree. C. before entering to the second stage membrane unit.
The membrane used in the first stage membrane unit and that used in
the second stage membrane unit in the two-stage membrane system
descried in the present invention are the same membranes with
propylene permeance of about 33-245 GPU, preferably about 66-195
GPU and high propylene/propane selectivity in the range of about
80-1000, preferably in the range of about 100-800.
[0031] The two-stage membrane system with the permeate of the
second stage membrane unit recycled back to the feed of the first
stage membrane unit as shown in FIG. 4 is capable of producing 98
KMTA (thousands of metric tons per annum) polymer grade propylene
product with at least 99.5 wt % propylene. All concentrations that
are discussed are regarding wt % propylene. The hydrocarbon feed
steam for the first stage membrane unit as shown in FIG. 4 has
about 70 wt % of propylene with a total volume of hydrocarbon
processed of 154 KMTA and the volume of the by-product in the
retentate of the second stage membrane unit is about 56 KMTA. In
FIG. 4, a feed 5 as described above is sent to a pretreatment zone
10 to provide a treated stream 11 that is heated by heater 20 and
enters membrane unit 22 to be separated into a permeate stream 25
and a retentate 30. Water vapor is added at 15 and 24. Retentate 30
is heated by heater 26 and passes through a second membrane unit 28
to be separated into second permeate stream 34 and second retentate
29. Second permeate stream is recycled to be combined with stream
11 to pass through the membrane units again.
[0032] In a fifth embodiment of the invention as shown in FIG. 5, a
typical treated hydrocarbon feed such as a low purity refinery
grade propylene comprising about 70 wt % propylene is vaporized and
heated to about 30-80.degree. C., preferably 45-65.degree. C. and
added with water to 40-100% humidity, preferably 50-90% humidity
before entering a three-stage membrane system from which the
permeate of the third stage membrane unit is combined with the
permeate of the second stage membrane unit, recompressed together,
and recycled to the feed of the first stage membrane unit to
provide a single polymer grade propylene (PGP with propylene purity
of about 99.5 wt % or 99.7 wt % or higher) product from the
permeate of the first stage membrane unit. The treated hydrocarbon
stream pressure at the membrane inlets for the first stage membrane
unit, the second stage membrane unit, and the third stage membrane
unit is about 80 to about 300 psig, preferably about 100 to about
240 psig. The treated hydrocarbon stream enters a three-stage
membrane system to produce a high purity single PGP product with
propylene purity of about 99.5 wt % or 99.7 wt % in the permeate of
the first stage membrane unit and the permeate of the third stage
membrane unit is combined with the permeate of the second stage
membrane unit, recompressed together, cooled, controlled at about
30-80.degree. C., preferably at about 45-65.degree. C., and
combined with the treated hydrocarbon feed to the first stage
membrane unit to provide a single polymer grade propylene (PGP with
propylene purity of about 99.7 wt % or higher) product from the
permeate of the first stage membrane unit. The total propylene
recovery is about 95.6%.
[0033] In FIG. 5, a feed 5 as described above is sent to a
pretreatment zone 10 to provide a treated stream 11 that is heated
by heater 20 and enters membrane unit 22 to be separated into a
permeate stream 25 and a retentate 30. Water vapor is added at 15,
24 and 50. Retentate 30 is heated by heater 26 to produce a heated
retentate 42 that passes through a second membrane unit 44 to be
separated into second permeate stream 46 and second retentate 48.
Second permeate stream is mixed with a third permeate stream 56
from third membrane unit 54. Retentate 48 is sent through heater 52
to pass through third membrane unit 54 to be separated into third
permeate stream 56 and third retentate 58. Third permeate stream 56
is combined with second permeate stream 46 to be recycled to
treated stream 11 to be sent through the membrane units again.
[0034] In the three-stage membrane system with the permeate of the
third stage membrane unit and the permeate of the second stage
membrane unit combined and recycled back to the feed of the first
stage membrane unit, the concentration of propylene in the
retentate of the third stage membrane is about 9.1 wt %. The
retentate of the first stage membrane and the retentate of the
second stage membrane unit are humidified to 40-100% humidity,
preferably 50-90% humidity and heated to about 30-80.degree. C.,
preferably 45-65.degree. C. before entering to the second stage
membrane unit and the third stage membrane unit, respectively. The
membrane used in the first stage membrane unit, that used in the
second stage membrane unit, and that used in the third stage
membrane unit in the three-stage membrane system as shown in FIG. 5
in the present invention are the same membranes with propylene
permeance of about 33-245 GPU, preferably about 66-195 GPU and high
propylene/propane selectivity in the range of about 80-1000,
preferably in the range of about 100-800. In some cases, additional
stages of membrane units are used and recombining permeates of the
additional stages with the permeates of the third and second stage
membrane units, recompressing the combined permeates, and recycling
the combined permeates to the feed of the first stage membrane unit
results in further improved overall propylene recovery. For
example, with the addition of a fourth stage membrane unit, the
recovery of propylene improves to 96.4% and propane rich product in
the retentate of the fourth stage membrane unit contains about 7.6
wt % of propylene.
[0035] The propane rich product, with 7-10% wt propylene, can be
compressed, cooled and further contacted with a finishing reactor,
or a hydrogenation reactor (UOP complete saturation process--CSP),
to reduce the concentration of propylene to less than or equal to
5% by volume and as low as 100 wt-ppm. The finishing reactor uses a
commercial CSP catalyst with controlled hydrogen addition and
residence time in the reactor to achieve targeted activity and
selectivity.
[0036] The three-stage membrane system with the permeate of the
third stage membrane unit and the permeate of the second stage
membrane unit combined and recycled back to the feed of the first
stage membrane unit as shown in FIG. 5 is capable of producing 102
KMTA polymer grade propylene product with at least 99.5 wt % or
99.7 wt % propylene. The hydrocarbon feed steam for the first stage
membrane unit as shown in FIG. 5 has about 70 wt % of propylene
with a total volume of hydrocarbon processed of 154 KMTA and the
volume of the by-product in the retentate of the third stage
membrane unit is about 52 KMTA.
[0037] The membranes used in the single stage membrane system, the
two-stage membrane systems without or with the recycle of the
permeate of the second stage membrane unit to the feed of the first
stage membrane unit, and the three-stage membrane systems without
or with the recycle of the permeates of the second stage membrane
unit and the third stage membrane unit to the feed of the first
stage membrane unit may be the membranes described in US
2018/0001277 A1; US 2018/0001268 A1; and U.S. application Ser. No.
15/599,258 filed May 18, 2017 incorporated herein in their
entireties.
[0038] Some of the facilitated transport membranes described in US
2018/0001277 A1 can be used in the membrane systems in the present
invention, wherein said facilitated transport membrane may comprise
a carboxylic acid functional group containing polyimide wherein the
carboxylic acid functional groups are ion-exchanged or chelated
with metal cations such as silver (I) or copper (I) cations. The
metal cation ion-exchanged or chelated carboxylic acid functional
group containing polyimide described in US 2018/0001277 A1
comprising a plurality of repeating units of formula (I)
##STR00001##
wherein X1 and X2 are selected from the group consisting of
##STR00002##
and mixtures thereof, and wherein X1 and X2 may be the same or
different from each other; wherein Y.sub.1--COOM is selected from
the group consisting of
##STR00003##
and mixtures thereof and wherein M is selected from silver (I)
cation or copper (I) cation; wherein Y2 is selected from the group
consisting of
##STR00004## ##STR00005##
and mixtures thereof, and --R'-- is selected from the group
consisting of
##STR00006##
and mixtures thereof, and --R''-- is selected from the group
consisting of --H, COCH.sub.3, and mixtures thereof, and M is
selected from silver (I) cation or copper (I) cation; wherein n and
m are independent integers from 2 to 500; and wherein n/m is in a
range of 1:0 to 1:10, and preferably n/m is in a range of 1:0 to
1:5.
[0039] Preferably, X1 and X2 are selected from the group consisting
of
##STR00007##
and mixtures thereof, and wherein X1 and X2 may be the same or
different from each other; preferably Y1-COOM is selected from the
group consisting of
##STR00008##
and mixtures thereof; preferably Y2 is selected from the group
consisting of
##STR00009##
and mixtures thereof.
[0040] The stable high performance facilitated transport membrane
described in US 2018/0001277 A1 comprising an asymmetric
integrally-skinned polymeric membrane wherein the pores on a
relatively porous, thin, dense skin layer of the membrane comprises
a hydrophilic polymer, a metal salt or a mixture of a metal salt
and hydrogen peroxide, wherein said asymmetric integrally-skinned
polymeric membrane comprises a relatively porous, thin, dense skin
layer as characterized by a CO.sub.2 permeance of at least 200 GPU
and a CO.sub.2 over CH.sub.4 selectivity between 1.1 and 10 at
50.degree. C. under 50-1000 psig, 10% CO.sub.2/90% CH.sub.4 mixed
gas feed pressure can be used as the membranes in the single stage
membrane system, the two-stage membrane systems without or with the
recycle of the permeate of the second stage membrane unit to the
feed of the first stage membrane unit, and the three-stage membrane
systems without or with the recycle of the permeates of the second
stage membrane unit and the third stage membrane unit to the feed
of the first stage membrane unit in the present invention. The
stable high performance facilitated transport membrane described in
US 2018/0001277 A1 used as the membranes in the membrane systems in
the present invention comprises a polymer selected from a group
consisting of a polyimide, a blend of two or more different
polyimides, and a blend of a polyimide and a polyethersulfone and
wherein the polyimide can be selected from the group consisting of
poly(2,2'-bis-(3,4-dicarboxyphenyl)hexafluoropropane
dianhydride-3,3',5,5'-tetramethyl-4,4'-methylene dianiline)
polyimide derived from a polycondensation reaction of
2,2'-bis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA)
with 3,3',5,5'-tetramethyl-4,4'-methylene dianiline (TMMDA),
poly(3,3',4,4'-diphenylsulfone tetracarboxylic
dianhydride-3,3',5,5'-tetramethyl-4,4'-methylene dianiline)
polyimide derived from the polycondensation reaction of
3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride (DSDA) with
TMMDA, poly(3,3',4,4'-benzophenone tetracarboxylic
dianhydride-pyromellitic
dianhydride-3,3',5,5'-tetramethyl-4,4'-methylene dianiline)
polyimide derived from the polycondensation reaction of a mixture
of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) and
pyromellitic dianhydride (PMDA) with TMMDA,
poly(3,3',4,4'-benzophenone tetracarboxylic
dianhydride-pyromellitic
dianhydride-2,4,6-trimethyl-1,3-phenylenediamine) polyimide derived
from the polycondensation reaction of a mixture of BTDA and PMDA
with 2,4,6-trimethyl-1,3-phenylenediamine (TMPDA),
poly(3,3',4,4'-benzophenone tetracarboxylic
dianhydride-pyromellitic
dianhydride-2,4,6-trimethyl-1,3-phenylenediamine-2,4-toluenediamine)
polyimide derived from the polycondensation reaction of a mixture
of BTDA and PMDA with a mixture of TMPDA and 2,4-toluenediamine
(2,4-TDA), and poly(3,3',4,4'-diphenylsulfone tetracarboxylic
dianhydride-3,3',5,5'-tetramethyl-4,4'-methylene
dianiline-4,4'-diamino-2-methylazobenzene) polyimide derived from
the polycondensation reaction of DSDA with a mixture of TMMDA and
4,4'-diamino-2-methylazobenzene (DAMAB).
[0041] The membranes used in all of the membrane systems in the
present invention may comprise a co-cast thin film composite flat
sheet membrane comprising an asymmetric porous non-selective
support layer and an asymmetric integrally skinned
polyimide-containing selective layer on top of said asymmetric
porous non-selective support layer wherein said asymmetric porous
non-selective support layer comprises a non-polyimide polymer or a
mixture of a non-polyimide polymer and a polyimide polymer and
wherein the weight ratio of said non-polyimide polymer to said
polyimide polymer in said mixture is in a range of 20:1 to 2:1 as
described in U.S. application Ser. No. 15/599,258.
[0042] The membranes used in the membrane systems in the present
invention may be the membranes as recently described in US
2017/0354918 A1; U.S. application Ser. No. 15/615,134 filed Jun. 6,
2017; and U.S. Provisional Application No. 62/549,820 filed Aug.
24, 2017 incorporated herein in their entireties.
[0043] The high selectivity facilitated transport membrane
disclosed in US 2017/0354918 A1 comprising a relatively
hydrophilic, very small pore, nanoporous support membrane, a
hydrophilic polymer inside the very small nanopores on the skin
layer surface of the support membrane, a thin, nonporous,
hydrophilic polymer layer coated on the surface of the support
membrane, and metal salts incorporated in the hydrophilic polymer
layer coated on the surface of the support membrane and the
hydrophilic polymer inside the very small nanopores can be used as
the membranes in the membrane systems described in the present
invention. The relatively hydrophilic, very small pore, nanoporous
support membrane used for the preparation of the new facilitated
transport membrane comprising a relatively hydrophilic, very small
pore, nanoporous support membrane, a hydrophilic polymer inside the
very small nanopores on the surface of the support membrane, a
thin, nonporous, hydrophilic polymer layer coated on the surface of
said support membrane, and metal salts incorporated in the
hydrophilic polymer layer coated on the surface of the support
membrane and said hydrophilic polymer inside the very small
nanopores disclosed in the present invention comprises a relatively
hydrophilic polymer selected from a group consisting of, but is not
limited to, polyethersulfone (PES), a blend of PES and polyimide,
cellulose acetate, cellulose triacetate, and a blend of cellulose
acetate and cellulose triacetate. The relatively hydrophilic, very
small pore, nanoporous support membrane described in the current
invention has an average pore diameter of less than 10 nm on the
membrane skin layer surface. The relatively hydrophilic, very small
pore, nanoporous support membrane described in the current
invention can be either asymmetric integrally skinned membrane or
thin film composite (TFC) membrane with either flat sheet (spiral
wound) or hollow fiber geometry.
[0044] The hydrophilic polymer inside the very small nanopores on
the surface of the relatively hydrophilic, very small pore,
nanoporous support membrane of the facilitated transport membrane
described in US 2017/0354918 A1 can be selected from, but is not
limited to, a group of hydrophilic polymers containing chitosan,
sodium carboxylmethyl-chitosan, carboxylmethyl-chitosan, hyaluronic
acid, sodium hyaluronate, carbopol, polycarbophil calcium,
poly(acrylic acid) (PAA), poly(methacrylic acid) (PMA), sodium
alginate, alginic acid, poly(vinyl alcohol) (PVA), poly(ethylene
oxide) (PEO), poly(ethylene glycol) (PEG), poly(vinylpyrrolidone)
(PVP), gelatin, carrageenan, sodium lignosulfonate, and mixtures
thereof.
[0045] The metal salts incorporated in the hydrophilic polymer
layer coated on the surface of said support membrane and the
hydrophilic polymer inside the very small nanopores of the
facilitated transport membrane described in US 2017/0354918 A1 are
preferred to be selected from silver salts or copper salts, such as
silver(I) nitrate or copper(I) chloride.
[0046] The dried, relatively hydrophilic, very small pore,
nanoporous support membrane comprising hydrophilic polymers inside
the very small nanopores on the membrane surface described in US
2017/0354918 A1 has carbon dioxide permeance of 800-10,000 GPU and
no carbon dioxide/methane selectivity at 50.degree. C. under 30-100
psig 10% CO2/90% CH.sub.4 mixed gas feed pressure.
[0047] The new facilitated transport membrane disclosed in U.S.
application Ser. No. 15/615,134 comprising a nanoporous
polyethersulfone/polyvinylpyrrolidone blend support membrane, a
hydrophilic polymer inside nanopores of said support membrane, a
hydrophilic polymer coating layer on a surface of the support
membrane and metal salts in the hydrophilic polymer coating layer
and in the hydrophilic polymer inside the nanopores of said support
membrane can also be used as the membranes in the membrane systems
described in the present invention.
[0048] A membrane comprising a polyethersulfone/polyethylene
oxide-polysilsesquioxane blend support membrane comprising a
polyethylene oxide-polysilsesquioxane polymer and a
polyethersulfone polymer; a hydrophilic polymer inside the pores on
the skin layer surface of the polyethersulfone/polyethylene
oxide-polysilsesquioxane blend support membrane; a hydrophilic
polymer coated on the skin layer surface of the
polyethersulfone/polyethylene oxide-polysilsesquioxane blend
support membrane, and metal salts incorporated in the hydrophilic
polymer coating layer and the skin layer surface pores of the
polyethersulfone/polyethylene oxide-polysilsesquioxane blend
support membrane can also be used as the membranes in the membrane
systems described in the present invention.
[0049] Any of the above membrane units, conduits, unit devices,
scaffolding, surrounding environments, zones or similar may be
equipped with one or more monitoring components including sensors,
measurement devices, data capture devices or data transmission
devices. Signals, process or status measurements, and data from
monitoring components may be used to monitor conditions in, around,
and on process equipment. Signals, measurements, and/or data
generated or recorded by monitoring components may be collected,
processed, and/or transmitted through one or more networks or
connections that may be private or public, general or specific,
direct or indirect, wired or wireless, encrypted or not encrypted,
and/or combination(s) thereof; the specification is not intended to
be limiting in this respect.
[0050] Signals, measurements, and/or data generated or recorded by
monitoring components may be transmitted to one or more computing
devices or systems. Computing devices or systems may include at
least one processor and memory storing computer-readable
instructions that, when executed by the at least one processor,
cause the one or more computing devices to perform a process that
may include one or more steps. For example, the one or more
computing devices may be configured to receive, from one or more
monitoring component, data related to at least one piece of
equipment associated with the process. The one or more computing
devices or systems may be configured to analyze the data. Based on
analyzing the data, the one or more computing devices or systems
may be configured to determine one or more recommended adjustments
to one or more parameters of one or more processes described
herein. The one or more computing devices or systems may be
configured to transmit encrypted or unencrypted data that includes
the one or more recommended adjustments to the one or more
parameters of the one or more processes described herein.
Specific Embodiments
[0051] While the following is described in conjunction with
specific embodiments, it will be understood that this description
is intended to illustrate and not limit the scope of the preceding
description and the appended claims.
[0052] A first embodiment of the invention is a process to separate
a hydrocarbon stream comprising a mixture of light olefins and
light paraffins, the process comprising sending the hydrocarbon
stream through a pretreatment unit to remove impurities selected
from the group consisting of sulfur compounds, arsine, phosphine,
acetylene, methylacetylene, and propadiene to produce a treated
hydrocarbon stream; vaporizing the treated hydrocarbon stream to
produce a gaseous treated hydrocarbon stream; adding liquid or
vapor water to the gaseous treated hydrocarbon stream; then
contacting the gaseous treated hydrocarbon stream to a membrane in
a membrane system comprising one or more membrane units to produce
a permeate stream comprising about 96 to 99.9 wt % light olefins
and a retentate stream comprising light paraffins. An embodiment of
the invention is one, any or all of prior embodiments in this
paragraph up through the first embodiment in this paragraph wherein
the water is added to the hydrocarbon stream before vaporizing it.
An embodiment of the invention is one, any or all of prior
embodiments in this paragraph up through the first embodiment in
this paragraph wherein the treated hydrocarbon stream is sent
through a selective hydrogenation unit to selectively hydrogenate
methyl acetylene, acetylene, and propadiene. An embodiment of the
invention is one, any or all of prior embodiments in this paragraph
up through the first embodiment in this paragraph wherein the
selective hydrogenation unit removes hydrogen to reduce the level
of hydrogen in the treated hydrocarbon stream to about 5 ppm or
less. An embodiment of the invention is one, any or all of prior
embodiments in this paragraph up through the first embodiment in
this paragraph wherein the selective hydrogenation unit contains a
catalyst selected from the group consisting of reduced forms of Pt,
Pd and Ni catalysts. An embodiment of the invention is one, any or
all of prior embodiments in this paragraph up through the first
embodiment in this paragraph wherein the hydrocarbon stream
comprises less than about 80 wt % light olefins. An embodiment of
the invention is one, any or all of prior embodiments in this
paragraph up through the first embodiment in this paragraph wherein
the hydrocarbon stream comprises less than about 70 wt % light
olefins. An embodiment of the invention is one, any or all of prior
embodiments in this paragraph up through the first embodiment in
this paragraph wherein the light olefins comprise ethylene or
propylene. An embodiment of the invention is one, any or all of
prior embodiments in this paragraph up through the first embodiment
in this paragraph wherein sufficient liquid or water vapor is added
to the gaseous treated hydrocarbon so that the gaseous treated
hydrocarbon stream has from 50 to 90% humidity when contacting the
membrane. An embodiment of the invention is one, any or all of
prior embodiments in this paragraph up through the first embodiment
in this paragraph wherein the membrane system comprises a single
stage membrane. An embodiment of the invention is one, any or all
of prior embodiments in this paragraph up through the first
embodiment in this paragraph wherein the membrane system comprises
a two stage membrane system wherein a retentate from a first
membrane unit is contacted to a second membrane unit to produce a
second permeate stream and a second retentate stream. An embodiment
of the invention is one, any or all of prior embodiments in this
paragraph up through the first embodiment in this paragraph wherein
the second permeate stream is recycled to the gaseous treated
hydrocarbon stream. An embodiment of the invention is one, any or
all of prior embodiments in this paragraph up through the first
embodiment in this paragraph wherein the membrane system comprises
a three stage membrane system wherein a retentate from a first
membrane unit is contacted to a second membrane unit to produce a
second permeate stream and a second retentate stream and the second
retentate stream is sent to a third membrane unit to produce a
third permeate stream and a third retentate. An embodiment of the
invention is one, any or all of prior embodiments in this paragraph
up through the first embodiment in this paragraph wherein the third
permeate is combined with said second permeate and recycled to the
gaseous treated hydrocarbon stream. An embodiment of the invention
is one, any or all of prior embodiments in this paragraph up
through the first embodiment in this paragraph wherein the membrane
system is operated at a temperature from about 30 to 80.degree. C.
An embodiment of the invention is one, any or all of prior
embodiments in this paragraph up through the first embodiment in
this paragraph wherein the hydrocarbon stream is at a pressure from
about 80 to about 300 psig before entering a membrane unit. An
embodiment of the invention is one, any or all of prior embodiments
in this paragraph up through the first embodiment in this paragraph
wherein the concentration of propylene in the retentate from a
single stage membrane system in about 40-45 wt %. An embodiment of
the invention is one, any or all of prior embodiments in this
paragraph up through the first embodiment in this paragraph wherein
a membrane used in the membrane system has a propylene permeance of
about 33-245 GPU and a propylene/propane selectivity in a range of
about 80-1000. An embodiment of the invention is one, any or all of
prior embodiments in this paragraph up through the first embodiment
in this paragraph wherein the permeate stream comprises about 99 to
99.5 wt % propylene. An embodiment of the invention is one, any or
all of prior embodiments in this paragraph up through the first
embodiment in this paragraph wherein the retentate comprises about
7 to 10 wt % propylene. An embodiment of the invention is one, any
or all of prior embodiments in this paragraph up through the first
embodiment in this paragraph wherein the process further comprises
at least one of: sensing at least one parameter of the process and
generating a signal from the sensing; sensing at least one
parameter of the process and generating data from the sensing;
generating and transmitting a signal; and generating and
transmitting data.
* * * * *