U.S. patent application number 12/610108 was filed with the patent office on 2010-02-25 for integrated oxygenate conversion and product cracking.
This patent application is currently assigned to UOP LLC. Invention is credited to Bryan K. Glover, Robert B. James, JR., Tom N. Kalnes, Daniel H. Wei.
Application Number | 20100048965 12/610108 |
Document ID | / |
Family ID | 38119696 |
Filed Date | 2010-02-25 |
United States Patent
Application |
20100048965 |
Kind Code |
A1 |
Kalnes; Tom N. ; et
al. |
February 25, 2010 |
Integrated Oxygenate Conversion and Product Cracking
Abstract
Improved processing of an oxygenate-containing feedstock for
increased production or yield of light olefins. Such processing
involves oxygenate conversion to olefins and subsequent cracking of
heavier olefins wherein at least a portion of the products from
each of the reactors is elevated in pressure, using a common
compressor, prior to being routed to a common product fractionation
and recovery section. In one particular embodiment, the cracked
product gas can be treated to remove acid gas therefrom. In another
embodiment, the olefin cracking reactor is a moving bed
reactor.
Inventors: |
Kalnes; Tom N.; (LaGrange,
IL) ; James, JR.; Robert B.; (Northbrook, IL)
; Wei; Daniel H.; (Naperville, IL) ; Glover; Bryan
K.; (Algonquin, IL) |
Correspondence
Address: |
HONEYWELL/UOP;PATENT SERVICES
101 COLUMBIA DRIVE, P O BOX 2245 MAIL STOP AB/2B
MORRISTOWN
NJ
07962
US
|
Assignee: |
UOP LLC
Des Plaines
IL
|
Family ID: |
38119696 |
Appl. No.: |
12/610108 |
Filed: |
October 30, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11293934 |
Dec 5, 2005 |
|
|
|
12610108 |
|
|
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|
Current U.S.
Class: |
585/315 |
Current CPC
Class: |
C07C 4/06 20130101; C10G
11/18 20130101; C07C 1/20 20130101; Y02P 30/42 20151101; Y02P 30/40
20151101; C10G 2400/20 20130101; C07C 1/24 20130101; C10G 3/42
20130101; Y02P 30/48 20151101; C10G 3/57 20130101; Y02P 30/20
20151101; C07C 1/20 20130101; C07C 11/02 20130101; C07C 1/24
20130101; C07C 11/02 20130101; C07C 4/06 20130101; C07C 11/02
20130101 |
Class at
Publication: |
585/315 |
International
Class: |
C07C 1/00 20060101
C07C001/00 |
Claims
1. A process for producing light olefins from an
oxygenate-containing feedstock, said process comprising: contacting
the oxygenate-containing feedstock in an oxygenate conversion
reactor with an oxygenate conversion catalyst and at reaction
conditions effective to convert the oxygenate-containing feedstock
to an oxygenate conversion product stream comprising fuel gas
hydrocarbons, light olefins, and C.sub.4+ hydrocarbons; compressing
at least a portion of the oxygenate conversion product stream via a
first compressor; treating the compressed oxygenate conversion
product stream in a gas concentration system to recover light
olefins and to form a C.sub.4+ hydrocarbon stream; contacting at
least a portion of the C.sub.4+ hydrocarbon stream in an olefin
cracking reactor with an olefin cracking catalyst and at reaction
conditions effective to convert C.sub.4 and C.sub.5 olefins therein
contained to a cracked olefins effluent stream comprising light
olefins; contacting at least a portion of the cracked olefins
effluent stream with an acid gas separation system; and returning
at least a portion of the cracked olefins effluent stream to the
first compressor for combination with the oxygenate conversion
product stream and subsequent treatment in the gas concentration
system.
2. The process of claim 1 wherein the oxygenate conversion reactor
is a fluidized bed reactor.
3. The process of claim 1 wherein the olefin cracking reactor is a
fixed bed reactor.
4. The process of claim 1 wherein the olefin cracking reactor is a
moving bed reactor.
5. The process of claim 4 wherein the olefin cracking catalyst is
continuously regenerated.
6. The process of claim 1 wherein the cracked olefins effluent
stream is separated into a first stream and a second stream,
wherein the first stream is the portion returned to the first
compressor for combination with the oxygenate conversion product
stream and subsequent treatment in the gas concentration
system.
7. The process of claim 6 wherein the second stream is introduced
to the gas concentration system without compression.
8. The process of claim 6 additionally comprising treating the
first stream to remove acid gas therefrom prior to return to the
first compressor.
9. The process of claim 1 wherein the oxygenate-containing
feedstock consists essentially of methanol.
10. The process of claim 1 wherein subsequent to the treating of
the compressed oxygenate conversion product stream, the process
additionally comprises fractionating the C.sub.4+ hydrocarbon
stream to form a process stream comprising C.sub.4+ through
C.sub.6- hydrocarbons and wherein the at least a portion of the
C.sub.4+ hydrocarbon stream contacted with the olefin cracking
catalyst comprises at least a portion of the process stream
comprising C.sub.4+ through C.sub.6- hydrocarbons.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a Continuation of prior copending
application Ser. No. 11/293,934 which was filed Dec. 5, 2005, the
contents of which are incorporated herein by reference thereto.
BACKGROUND OF THE INVENTION
[0002] This invention relates generally to the conversion of
oxygenates to olefins and, more particularly, to light olefins.
[0003] Light olefins serve as feed materials for the production of
numerous chemicals. Light olefins have traditionally been produced
through the processes of steam or catalytic cracking. The limited
availability and high cost of petroleum sources, however, has
resulted in a significant increase in the cost of producing light
olefins from such petroleum sources.
[0004] The search for alternative materials for light olefin
production has led to the use of oxygenates such as alcohols and,
more particularly, to the use of methanol, ethanol, and higher
alcohols or their derivatives. Molecular sieves such as microporous
crystalline zeolite and non-zeolitic catalysts, particularly
silicoaluminophosphates (SAPO), are known to promote the conversion
of oxygenates to hydrocarbon mixtures, particularly hydrocarbon
mixtures composed largely of light olefins.
[0005] The amounts of light olefins resulting from such processing
can be further increased by reacting, i.e., cracking, heavier
hydrocarbon products, particularly heavier olefins such as C.sub.4
and C.sub.5 olefins, to light olefins. For example, commonly
assigned, U.S. Pat. No. 5,914,433 to Marker, the entire disclosure
of which is incorporated herein by reference, discloses a process
for the production of light olefins comprising olefins having from
2 to 4 carbon atoms per molecule from an oxygenate feedstock. The
process comprises passing the oxygenate feedstock to an oxygenate
conversion zone containing a metal aluminophosphate catalyst to
produce a light olefin stream. A propylene and/or mixed butylene
stream is fractionated from said light olefin stream and cracked to
enhance the yield of ethylene and propylene products. This
combination of light olefin product and propylene and butylene
cracking in a riser cracking zone or a separate cracking zone
provides flexibility to the process which overcomes the equilibrium
limitations of the aluminophosphate catalyst. In addition, the
invention provides the advantage of extended catalyst life and
greater catalyst stability in the oxygenate conversion zone.
[0006] Mechanical devices are used for driving fluids to
appropriate locations at desired pressures. A pump is a mechanical
device or machine that is used to force a liquid phase material
from one pressure to a higher pressure. The mechanical work
performed by a pump is proportional to the volume of the liquid
being pumped times the differential pressure which is outlet
pressure minus inlet pressure. Some of the mechanical work is
expended in transferring the liquid from one location to another.
Pumps are not typically sufficiently powerful to change the volume
of the liquid being pumped. A compressor is a mechanical device or
machine that is used to force a vapor phase material from one
pressure to a higher pressure. The mechanical work performed by a
compressor is proportional to the volume of the vapor being pumped
times the differential pressure. Compressors typically decrease the
volume of the vapor being pumped. Material in the liquid phase is
always much more dense than material in the vapor phase. For the
same mass of material, the work required to pump liquid is always
much less than the work required to pump vapor via compressor.
[0007] Further improvements such as relating to reducing or
minimizing system processing costs and complexity, however, are
desired and are being sought.
[0008] In view thereof, there is a need and a demand for improved
processing and systems for the conversion of oxygenates to olefins
and, more particularly, for such processing and systems such as to
result in an increase in the relative amount of light olefins.
SUMMARY OF THE INVENTION
[0009] A general object of the invention is to provide or result in
improved processing of an oxygenate-containing feedstock to light
olefins.
[0010] A more specific objective of the invention is to overcome
one or more of the problems described above.
[0011] The general object of the invention can be attained, at
least in part, through a process for producing light olefins from
an oxygenate-containing feedstock. In accordance with one preferred
embodiment, such a process involves contacting the
oxygenate-containing feedstock in an oxygenate conversion reactor
with an oxygenate conversion catalyst and at reaction conditions
effective to convert the oxygenate-containing feedstock to an
oxygenate conversion product stream comprising fuel gas
hydrocarbons, light olefins, and C.sub.4+ hydrocarbons. At least a
portion of the oxygenate conversion product stream is subsequently
compressed via a first compressor. The compressed oxygenate
conversion product stream is treated in a gas concentration system
to recover light olefins and to form a C.sub.4+ hydrocarbon stream.
At least a portion of the C.sub.4+ hydrocarbon stream is contacted
in an olefin cracking reactor with an olefin cracking catalyst and
at reaction conditions effective to convert C.sub.4 and C.sub.5
olefins therein contained to a cracked olefins effluent stream
comprising light olefins. At least a portion of the cracked olefins
effluent stream is returned to the first compressor for combination
with the oxygenate conversion product stream and subsequent
treatment in the gas concentration system.
[0012] The prior art generally fails to provide processing of
oxygenates to olefins, particularly such as to result in an
increase in the relative amount of light olefins, and which
processing is one or more as simple, effective, as economic as may
be desired.
[0013] In another embodiment, there is provided a process for
producing light olefins from a methanol-containing feedstock. The
process involves contacting the methanol-containing feedstock in a
methanol conversion reactor fluidized reaction zone with a methanol
conversion catalyst and at reaction conditions effective to convert
the methanol-containing feedstock to a methanol conversion product
stream comprising fuel gas hydrocarbons, light olefins, and
C.sub.4+ hydrocarbons. At least a portion of the methanol
conversion product stream is subsequently compressed via a first
compressor. The compressed methanol conversion product stream it
treated in a gas concentration system to recover light olefins and
to form a fuel gas hydrocarbon stream and a C.sub.4+ hydrocarbon
stream. The C.sub.4+ hydrocarbon stream is fractionated to form a
process stream comprising C.sub.4+ through C.sub.6- hydrocarbons
and a purge stream comprising C.sub.7+ hydrocarbons. The process
stream is contacted in an olefin cracking reactor with an olefin
cracking catalyst and at reaction conditions effective to convert
C.sub.4 and C.sub.5 olefins therein contained to a cracked olefins
effluent stream comprising light olefins. The cracked olefins
effluent stream is separated into a first stream comprising C.sub.1
and C.sub.2 hydrocarbons and a second stream comprising a remainder
of the olefin cracking product stream. The first stream is returned
to the first compressor for combination with the oxygenate
conversion product stream and subsequent treatment in the gas
concentration system and the second stream is introduced to the gas
concentration system without compression.
[0014] There is also provided a system for converting oxygenates to
light olefins. In accordance with one embodiment, a reactor is
provided for contacting an oxygenate-containing feedstream with
catalyst and converting the oxygenate-containing feedstream to an
oxygenate conversion product stream comprising fuel gas
hydrocarbons, light olefins, and C.sub.4+ hydrocarbons. A first
compressor is provided to compress at least a portion of the
oxygenate conversion product stream to form a compressed oxygenate
conversion product stream. A gas concentration system is provided
to treat the compressed oxygenate conversion product stream to
recover light olefins and to form a C.sub.4+ hydrocarbon stream.
The system further includes a reactor for contacting at least a
portion of the C.sub.4+ hydrocarbon stream with catalyst and
converting C.sub.4 and C.sub.5 olefins therein contained to a
cracked olefin effluent stream comprising light olefins. A first
return line is provided wherein at least a portion of the cracked
olefin effluent stream is introduced into the first compressor and
subsequently processed through the gas concentration system.
[0015] As used herein, references to "light olefins" are to be
understood to generally refer to C.sub.2 and C.sub.3 olefins, i.e.,
ethylene and propylene.
[0016] Other objects and advantages will be apparent to those
skilled in the art from the following detailed description taken in
conjunction with the appended claims and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a simplified schematic diagram of a process for
the conversion of an oxygenate-containing feedstock to olefins in
accordance with one embodiment.
[0018] FIG. 2 is a simplified schematic diagram of a process for
the conversion of an oxygenate-containing feedstock to olefins in
accordance with another embodiment.
[0019] FIG. 3 is a simplified schematic diagram of a process for
the conversion of an oxygenate-containing feedstock to olefins in
accordance with yet another embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Oxygenate-containing feedstock can be converted to light
olefins in a catalytic reaction and heavier hydrocarbons (e.g.,
C.sub.4+, hydrocarbons) formed during such processing can be
subsequently cracked to increase the light olefins (e.g., C.sub.2
and C.sub.3 olefins) produced or resulting therefrom. In accordance
with a preferred embodiment, at least a portion of the oxygenate
conversion product stream and at least a portion of the olefin
cracking product stream are elevated in pressure, together or
separately, through the same compressor prior to being routed
through an appropriate gas concentration system.
[0021] FIG. 1 schematically illustrates a system, generally
designated by the reference numeral 10, for the conversion of an
oxygenate-containing feedstock to olefins in accordance with one
embodiment.
[0022] More particularly, an oxygenate-containing feedstock 12 such
as generally composed of light oxygenates such as one or more of
methanol, ethanol, dimethyl ether, diethyl ether, or mixtures
thereof, is introduced into an oxygenate conversion reactor section
14 wherein the oxygenate-containing feedstock contacts with an
oxygenate conversion catalyst at reaction conditions effective to
convert the oxygenate-containing feedstock to an oxygenate
conversion product stream comprising fuel gas hydrocarbons, light
olefins, and C.sub.4+ hydrocarbons, in a manner as is known in the
art, such as, for example, utilizing a fluidized bed reactor.
[0023] As will be appreciated by those skilled in the art and
guided by the teachings herein provided, such a feedstock may be
commercial grade methanol, crude methanol or any combination
thereof Crude methanol may be an unrefined product from a methanol
synthesis unit. Those skilled in that art and guided by the
teachings herein provided will understand and appreciate that in
the interest of factors such as improved catalyst stability,
embodiments utilizing higher purity methanol feeds may be
preferred. Thus, suitable feeds may comprise methanol or a methanol
and water blend, with possible such feeds having a methanol content
of between about 65% and about 100% by weight, preferably a
methanol content of between about 80% and about 100% by weight and,
in accordance one preferred embodiment, a methanol content of
between about 95% and about 100% by weight
[0024] A methanol-to-olefin unit designed to process about
2,500,000 metric tons per year of 95 wt. % methanol may have a feed
rate of preferably between about 1500 and about 4000 kMTA and more
preferably between about 2000 and about 3500 kMTA. The feedstream
may comprise between about 0 and about 35 wt. % and more preferably
between about 5 and about 30 wt. % water. The methanol in the feed
stream may comprise between about 70 and about 100 wt. % and more
preferably between about 75 and about 95 wt. % of the feedstream.
The ethanol in the feedstream may comprise between about 0.01 and
about 0.5 wt. % and more typically between about 0.1 and about 0.2
wt. % of the feedstream although higher concentrations may be
beneficial. When methanol is the primary component in the
feedstream, the higher alcohols in the feedstream may comprise
between about 200 and about 2000 wppm and more typically between
about 500 and about 1500 wppm. Additionally, when methanol is the
primary component in the feedstream, dimethyl ether in the
feedstream may comprise between about 100 and about 20,000 wppm and
more typically between about 200 and about 10,000 wppm.
[0025] Reaction conditions for the conversion of oxygenates to
light olefins are known to those skilled in the art. Preferably, in
accordance with particular embodiments, reaction conditions
comprise a temperature between about 200.degree. and about
700.degree. C., more preferably between about 300.degree. and
600.degree. C., and most preferably between about 400.degree. and
about 5500 C. As will be appreciated by those skilled in the art
and guided by the teachings herein provided, the reactions
conditions are generally variable such as dependent on the desired
products. For example, if increased ethylene production is desired,
then operation at a reactor temperature between about 475.degree.
and about 550.degree. C. and more preferably between about
500.degree. and about 520.degree. C., may be preferred. If
increased propylene production is desired, then operation at a
reactor temperature between about 350.degree. and about 475.degree.
C. and more preferably between about 400.degree. and about
430.degree. C. may be preferred. The light olefins produced can
have a ratio of ethylene to propylene of between about 0.5 and
about 2.0 and preferably between about 0.75 and about 1.25. If a
higher ratio of ethylene to propylene is desired, then the reaction
temperature is higher than if a lower ratio of ethylene to
propylene is desired. The preferred feed temperature range is
between about 120.degree. and about 210.degree. C. More preferably
the feed temperature range is between about 180.degree. and
210.degree. C. In accordance with one preferred embodiment, the
temperature is desirably maintained below 210.degree. C. to avoid
or minimize thermal decomposition.
[0026] The oxygenate conversion reactor section 14 produces or
results in an oxygenate conversion product or effluent stream 16
generally comprising fuel gas hydrocarbons, light olefins, and
C.sub.4+ hydrocarbons. The oxygenate conversion reactor section 14
may also, as shown, produce or result in a wastewater stream 20,
such as, for example, may contain low levels of unreacted alcohols
as well as small amounts of oxygenated byproducts such as low
molecular weight aldehydes and organic acids, and such as may be
appropriately treated and disposed or recycled.
[0027] The oxygenate conversion product stream 16 and a recycle
stream 22, such as described in greater detail below, and such as
together form a process stream designated by the reference numeral
23, are appropriately processed through a compressor 24. The
resulting compressed oxygenate conversion product stream 26 and, if
desired, a recycle stream 30, described in greater detail below,
and such as together form a process stream designated by the
reference numeral 31, are introduced into an appropriate gas
concentration system 32.
[0028] Gas concentration systems such as used for the processing of
the products resulting from such oxygenate conversion processing
are well known to those skilled in the art and do not generally
form limitations on the broader practice of the invention as those
skilled in the art and guided by the teachings herein provided will
appreciate.
[0029] In the gas concentration system 32, the process stream 31
such as constituting the compressed oxygenate conversion product
stream 26 and, if used, the recycle stream 30, is processed to
provide a fuel gas stream 34, an ethylene stream 36, a propylene
stream 40 and a mixed C.sub.4+ hydrocarbon stream 42, such as
generally composed of butylene and heavier hydrocarbons.
[0030] The mixed C.sub.4+ hydrocarbon stream 42 is subjected to a
fractionation section 44 such as to form a purge stream 46 such as
generally comprising C.sub.7+ hydrocarbons and a process stream 50
such as generally comprising C.sub.4, C.sub.5 and C.sub.6
hydrocarbons. At least a portion of the process stream 50, e.g.,
the process stream portion 52, is introduced into an olefin
cracking reactor section 54, such as in the form of a fixed bed
reactor, as is known in the art and wherein the process stream
portion 52 contacts with an olefin cracking catalyst and at
reaction conditions, in a manner as is known in the art, effective
to convert C.sub.4 and C.sub.5 olefins therein contained to a
cracked olefins effluent stream 56 comprising light olefins.
[0031] A purge stream 60 is shown whereby C.sub.4-C.sub.6 paraffin
compounds and the like may desirably be purged from the material
stream being processed in the system 10, in a manner such as known
in the art. As will be appreciated by those skilled in the art and
guided by the teachings herein provided, such compounds generally
do not convert very well in olefin cracking reactors. Consequently,
such purging can avoid the undesirable build-up of such compounds
within the process system 10.
[0032] The cracked olefins effluent stream 56 is processed through
a cooler 62 to form a process stream 64. The process stream 64 is
then processed through a gas-liquid separator 66 to form a recycle
stream of gaseous material, such as constituting the
above-identified recycle stream 22 and such as generally comprising
C.sub.1 and C.sub.2 hydrocarbons. As shown, the recycle stream 22
can be combined with the oxygenate conversion product stream 16 and
returned to the compressor 24. The gas-liquid separator 66 also
forms a process stream 70 such as constituting the remainder of the
cracked olefins effluent such as generally comprising liquid
material and such as may be conveyed via a pump 72 such as to
constitute the recycle stream 30, identified above, and such as for
combination with the compressed oxygenate conversion product stream
26 and subsequent processing through the gas concentration system
32. In accordance with the illustrated embodiment, the recycle
stream 30 can desirably be introduced to the gas concentration
system 32 without first undergoing compression.
[0033] The system 10 desirably serves to increase or maximize the
conversion of the oxygenate feedstock to light olefins while
reducing or minimizing the production of C.sub.4+ liquid. Further
such an embodiment desirably reduces or minimizes capital costs by
utilizing a single or common compressor for the treatment of the
effluent from the two reactor sections, i.e., the oxygenate
conversion reactor and the olefin cracking reactor. Such embodiment
still further reduces or minimizes capital costs by utilizing a
single or common gas concentration system, such as composed of
appropriate product fractionation and recovery sections, for the
treatment of the effluent from the two reactor sections.
[0034] FIG. 2 illustrates a system, generally designated by the
reference numeral 210, for the conversion of an
oxygenate-containing feedstock to olefins in accordance with
another embodiment. The system 210 is generally similar to the
system 10 shown in FIG. 1 and described above.
[0035] More particularly, an oxygenate-containing feedstock 212 is
introduced into an oxygenate conversion reactor section 214 wherein
the oxygenate-containing feedstock contacts with an oxygenate
conversion catalyst and at reaction conditions effective to convert
the oxygenate-containing feedstock to an oxygenate conversion
product stream comprising fuel gas hydrocarbons, light olefins, and
C.sub.4+ hydrocarbons, in a manner as is known in the art.
[0036] The oxygenate conversion reactor section 214 produces or
results in an oxygenate conversion product stream 216 generally
comprising fuel gas hydrocarbons, light olefins, and C.sub.4+
hydrocarbons. The oxygenate conversion reactor section 214 may
also, as shown, produce or result in wastewater stream 220, such as
may be appropriately treated and disposed or recycled.
[0037] The oxygenate conversion product stream 216 and a recycle
stream 222, such as described in greater detail below, and such as
together form a process stream designated by the reference numeral
223, are appropriately processed through a compressor 224. The
resulting compressed oxygenate conversion product stream 226 and,
if desired, a recycle stream 230, described in greater detail
below, and such as together form a process stream designated by the
reference numeral 231, are introduced into an appropriate gas
concentration system 232.
[0038] In the gas concentration system 232, the process stream 231
such as constituting the compressed oxygenate conversion product
stream 226 and, if used, the recycle stream 230, is processed to
provide a fuel gas stream 234, an ethylene stream 236, a propylene
stream 240 and a mixed C.sub.4+ hydrocarbon stream 242, such as
generally composed of butylene and heavier hydrocarbons.
[0039] The mixed C.sub.4+ hydrocarbon stream 242 is subjected to a
fractionation section 244 such as to form a purge stream 246 such
as generally comprising C.sub.7+ hydrocarbons and a process stream
250 such as generally comprising C.sub.4, C.sub.5 and C.sub.6
hydrocarbons. At least a portion of the process stream 250, e.g.,
the process stream portion 252, is introduced into an olefin
cracking reactor section 254, such as in the form of a fixed bed
reactor, as is known in the art and wherein the process stream
portion 252 contacts with an olefin cracking catalyst and at
reaction conditions, in a manner as is known in the art, effective
to convert C.sub.4 and C.sub.5 olefins therein contained to a
cracked olefins effluent stream 256 comprising light olefins.
[0040] Similar to the system 10 described above, a purge stream 260
is shown whereby C.sub.4-C.sub.6 paraffin compounds and the like
may desirably be purged from the material stream being processed in
the system 210, such as in a manner known in the art.
[0041] The cracked olefins effluent stream 256 is processed through
a cooler 262 to form a process stream 264. The process stream 264
is then processed through a gas-liquid separator 266 to form a
stream 268 of gaseous material and a stream 270 such as
constituting the remainder of the cracked olefins effluent such as
generally comprising liquid material and such as may be conveyed
via a pump 272 such as to constitute the recycle stream 230,
identified above. As shown, the recycle stream 230 can desirably be
introduced to the gas concentration system 232 without first
undergoing compression.
[0042] The system 210 primarily differs from the system 10,
described above, by the inclusion of an acid gas separation section
276. The acid gas separation section 276 treats the stream 268 of
gaseous material to remove acid gas therefrom such as may normally
be present therein in relatively minor or trace amounts. With such
acid gas removal, a recycle stream of gaseous material is formed,
such as constituting the above-identified recycle stream 222 and
such as generally comprising C.sub.1 and C.sub.2 hydrocarbons. Such
acid gas removal can be realized by various manners known in the
art and can desirably occur prior to return of the material to the
compressor 224. Such acid gas removal can significantly facilitate
downstream material handling and permit the utilization less costly
processing hardware. For example, through such acid gas removal,
H.sub.2S can desirably be kept out of the various process and
product streams and the need for the use of more expensive
metallurgy in product compressors and various downstream equipment
can be minimized or preferably avoided.
[0043] While embodiments utilizing a fixed bed olefin cracking
reactor unit have been described above, those skilled in the art
and guided by the teachings herein provided will appreciate that
the broader practice of the invention is not necessarily so
limited. To that end, reference is now made to FIG. 3 which
illustrates a system, generally designated by the reference numeral
310, for the conversion of an oxygenate-containing feedstock to
olefins in accordance with yet another embodiment and wherein an
olefin cracking reactor unit having the form of a moving bed
reactor is utilized. The system 310 is generally similar to the
system 10 shown in FIG. 1 and described above.
[0044] More particularly, an oxygenate-containing feedstock 312 is
introduced into an oxygenate conversion reactor section 314 wherein
the oxygenate-containing feedstock contacts with an oxygenate
conversion catalyst and at reaction conditions effective to convert
the oxygenate-containing feedstock to an oxygenate conversion
product stream comprising fuel gas hydrocarbons, light olefins, and
C.sub.4+ hydrocarbons, in a manner as is known in the art.
[0045] The oxygenate conversion reactor section 314 produces or
results in an oxygenate conversion product stream 316 generally
comprising fuel gas hydrocarbons, light olefins, and C.sub.4+
hydrocarbons. The oxygenate conversion reactor section 314 may
also, as shown, produce or result in wastewater stream 320, such as
may be appropriately treated and disposed or recycled.
[0046] The oxygenate conversion product stream 316 and a recycle
stream 322, such as described in greater detail below, and such as
together form a process stream designated by the reference numeral
323, are appropriately processed through a compressor 324. The
resulting compressed oxygenate conversion product stream 326 and,
if desired, a recycle stream 330, described in greater detail
below, and such as together form a process stream designated by the
reference numeral 331, are introduced into an appropriate gas
concentration system 332.
[0047] In the gas concentration system 332, the process stream 331
such as constituting the compressed oxygenate conversion product
stream 326 and, if used, the recycle stream 330, is processed to
provide a fuel gas stream 334, an ethylene stream 336, a propylene
stream 340 and a mixed C.sub.4+ hydrocarbon stream 342, such as
generally composed of butylene and heavier hydrocarbons.
[0048] The mixed C.sub.4+ hydrocarbon stream 342 is subjected to a
fractionation section 344 such as to form a purge stream 346 such
as generally comprising C.sub.7+ hydrocarbons and a process stream
350 such as generally comprising C.sub.4, C.sub.5 and C.sub.6
hydrocarbons. At least a portion of the process stream 350, e.g.,
the process stream portion 352, is introduced into an olefin
cracking reactor section 354 wherein the process stream portion 352
contacts with an olefin cracking catalyst and at reaction
conditions, in a manner as is known in the art, effective to
convert C.sub.4 and C.sub.5 olefins therein contained to a cracked
olefins effluent stream 356 comprising light olefins.
[0049] Similar to the system 110 described above, a purge stream
360 is shown whereby C.sub.4-C.sub.6 paraffin compounds and the
like may desirably be purged from the material stream being
processed in the system 310, such as in a manner known in the art,
and such as to avoid the undesirable build-up of such compounds
within the process system 310.
[0050] The cracked olefins effluent stream 356 is processed through
a cooler 362 to form a process stream 364. The process stream 364
is then processed through a gas-liquid separator 366 to form a
recycle stream of gaseous material, such as constituting the
above-identified recycle stream 322 and such as generally
comprising C.sub.1 and C.sub.2 hydrocarbons. The gas-liquid
separator 366 also forms a process stream 370 such as constituting
the remainder of the cracked olefins effluent such as generally
comprising liquid material and such as may be conveyed via a pump
372 such as to constitute the recycle stream 330, identified above,
and such as for combination with the compressed oxygenate
conversion product stream 326 and subsequent processing through the
gas concentration system 332. As shown, the recycle stream 330 can
desirably be introduced to the gas concentration system 332 without
first undergoing compression.
[0051] The system 310 primarily differs from the system 10,
described above, by requiring that the olefin cracking reactor
section 354 includes a moving bed reactor 390 which allows at least
a portion of the catalyst from the moving bed reactor 390 to be
regenerated on a continuous or semi-continuous basis in a separate
but integrated regeneration zone 392.
[0052] The incorporation and use of moving bed (radial flow)
reactor with continuous or semi-continuous catalyst regeneration
for the cracking of the heavy recycle olefins can desirably serve
to minimize the capital costs for the processing arrangement. For
example, utilization of such a moving bed reactor with a continuous
catalyst regenerator can desirably allow the associated olefin
cracking reactor to operate at a higher average conversion as
compared to a typical swing bed reactor system. In addition, the
reactor section effluent from such a moving bed reactor desirably
provides or results in a steadier composition such as may desirably
simplify the design and operation of downstream fractionators.
[0053] If desired, the system 310 can be appropriately modified to
incorporate an acid gas separation section (not shown), such as
identified and described above relative to the system 210, shown in
FIG. 2.
[0054] While the invention has been described above making specific
reference to the processing of an oxygenate-containing feedstock
comprising light oxygenates such as one or more of methanol,
ethanol, dimethyl ether, diethyl ether, or mixtures thereof, those
skilled in the art and guided by the teachings herein provided will
appreciate that the broader practice of the invention is not
necessarily so limited. More particularly, suitable
"oxygenate-containing" feedstocks employed in the practice of the
invention are to be understood to include alcohols, ethers and
carbonyl compounds (aldehydes, ketones, carboxylic acids and the
like). Moreover, such suitable oxygenate-containing feedstocks
preferably contain from 1 to about 10 carbon atoms and, more
preferably, contains from 1 to about 4 carbon atoms. Suitable
reactants include lower straight or branched chain alkanols, their
unsaturated counterparts. Representatives of suitable oxygenate
compounds include: methanol; dimethyl ether; ethanol; diethyl
ether; methyl ethyl ether; formaldehyde; dimethyl ketone; acetic
acid; and mixtures thereof.
[0055] Embodiments, such as described above, desirably provide or
result in improved processing of oxygenates to olefins,
particularly such as to result in an increase in the relative
amount of light olefins, and which processing is desirably more
simple, effective, and/or economic than heretofore reasonably
possible. In accordance with particular such embodiments, an
oxygenate-containing feedstock can be converted to light olefins in
a catalytic reaction and heavier hydrocarbons (e.g., C.sub.4+
hydrocarbons) formed during such processing can be subsequently
cracked to increase the light olefins (e.g., C.sub.2 and C.sub.3
olefins) produced or resulting therefrom, with at least a portion
of the oxygenate conversion product stream and at least a portion
of the oxygenate conversion product stream being elevated in
pressure, together or separately, through the same compressor prior
to being routed through an appropriate gas concentration
system.
[0056] The invention illustratively disclosed herein suitably may
be practiced in the absence of any element, part, step, component,
or ingredient which is not specifically disclosed herein.
[0057] While in the foregoing detailed description this invention
has been described in relation to certain preferred embodiments
thereof, and many details have been set forth for purposes of
illustration, it will be apparent to those skilled in the art that
the invention is susceptible to additional embodiments and that
certain of the details described herein can be varied considerably
without departing from the basic principles of the invention.
* * * * *