U.S. patent application number 15/435039 was filed with the patent office on 2018-08-16 for process for recovery of light alkyl mono-aromatic compounds from heavy alkyl aromatic and alkyl-bridged non-condensed alkyl aromatic compounds.
The applicant listed for this patent is Saudi Arabian Oil Company. Invention is credited to Bruce Richard Beadle, Rakan Sulaiman Bilaus, Robert P. Hodgkins, Omer R. Koseoglu, Vinod Ramaseshan.
Application Number | 20180230070 15/435039 |
Document ID | / |
Family ID | 61283432 |
Filed Date | 2018-08-16 |
United States Patent
Application |
20180230070 |
Kind Code |
A1 |
Beadle; Bruce Richard ; et
al. |
August 16, 2018 |
PROCESS FOR RECOVERY OF LIGHT ALKYL MONO-AROMATIC COMPOUNDS FROM
HEAVY ALKYL AROMATIC AND ALKYL-BRIDGED NON-CONDENSED ALKYL AROMATIC
COMPOUNDS
Abstract
Embodiments in the present disclosure describe a process for
recovery of lighter mono-aromatic compounds from a stream
containing alkyl bridged non-condensed alkyl multi-aromatic
compounds by conversion to non-condensed alkyl mono-aromatic
compounds. The process includes supplying, to a reactor, a
hydrocarbon feedstock containing alkyl bridged non-condensed alkyl
aromatic compounds and a hydrogen stream. The process further
includes allowing the alkyl-bridged non-condensed alkyl
multi-aromatic compounds to react with hydrogen in the presence of
a suitable catalyst to produce alkyl mono-aromatic compounds. The
process may include processing the alkyl mono-aromatic compounds to
produce valuable products, such as para-xylene. Various other
embodiments are disclosed and claimed.
Inventors: |
Beadle; Bruce Richard;
(Dhahran, SA) ; Ramaseshan; Vinod; (Ras Tanura,
SA) ; Bilaus; Rakan Sulaiman; (Dhahran, SA) ;
Koseoglu; Omer R.; (Dhahran, SA) ; Hodgkins; Robert
P.; (Dhahran, SA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Saudi Arabian Oil Company |
Dhahran |
|
SA |
|
|
Family ID: |
61283432 |
Appl. No.: |
15/435039 |
Filed: |
February 16, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C07C 2529/16 20130101;
C07C 4/24 20130101; C07C 4/26 20130101; C07C 4/26 20130101; C07C
15/00 20130101; C07C 4/26 20130101; C07C 15/08 20130101 |
International
Class: |
C07C 4/24 20060101
C07C004/24 |
Claims
1. A process for recovery of alkyl mono-aromatic compounds, the
process comprising the steps of: supplying, to a reactor, a feed
stream containing one or more of heavy alkyl aromatic compounds and
alkyl-bridged non-condensed alkyl multi-aromatic compounds;
supplying, to the reactor, a hydrogen stream; allowing the feed
stream and the hydrogen stream to react in presence of a catalyst
under specific reaction conditions to produce a product stream
containing one or more alkyl mono-aromatic compounds; and
recovering, from the reactor, the product stream for a downstream
process, wherein the alkyl-bridged non-condensed alkyl
multi-aromatic compounds include at least two benzene rings
connected by an alkyl bridge group having at least two carbons,
wherein the benzene rings are connected to different carbons of the
alkyl bridge group.
2. The process of claim 1, wherein the feed stream comprises
C.sub.9+ alkyl aromatic compounds obtained from a xylene rerun
column.
3. The process of claim 1, wherein the feed stream is undiluted by
a solvent.
4. The process of claim 1, wherein the hydrogen stream is combined
with the feed stream before being supplied to the reactor.
5. The process of claim 1, wherein the hydrogen stream is comprised
of a recycled hydrogen stream and a makeup hydrogen stream.
6. The process of claim 1, wherein the hydrogen stream comprises at
least 70% hydrogen by weight.
7. The process of claim 1, wherein the catalyst is presented as a
catalyst bed in the reactor.
8. The process of claim 7, wherein a portion of the hydrogen stream
is fed to the catalyst bed in the reactor to quench the catalyst
bed.
9. The process of claim 7, wherein the catalyst bed is comprised of
two or more catalyst beds.
10. The process of claim 1, wherein the catalyst includes a support
being at least one member of the group consisting of silica,
alumina, and combinations thereof, and further includes an acidic
component being at least one member of the group consisting of
amorphous silica-alumina, zeolite, and combinations thereof.
11. The process of claim 10, wherein the catalyst includes an IUPAC
Group 8-10 metal being at least one member of the group consisting
of iron, cobalt, and nickel, and combinations thereof and further
includes an IUPAC Group 6 metal being at least one member of the
group consisting of molybdenum and tungsten, and combinations
thereof.
12. The process of claim 11, wherein the IUPAC 8-10 metal is 2 to
20 percent by weight of the catalyst and the IUPAC Group 6 metal is
1 to 25 percent by weight of the catalyst.
13. The process of claim 1, wherein the catalyst is comprised of
nickel, molybdenum, ultrastable Y-type zeolite, and .gamma.-alumina
support.
14. The process of claim 1, wherein specific reaction conditions
include an operating temperature of the reactor being in the range
of 200 to 450.degree. C.
15. The process of claim 14, wherein the operating temperature of
the reactor is about 300.degree. C.
16. The process of claim 14, wherein the operating temperature of
the reactor is about 350.degree. C.
17. The process of claim 1, wherein specific reaction conditions
include an hydrogen partial pressure of the reactor being in the
range of 5 to 50 bar gauge.
18. The process of claim 17, wherein the hydrogen partial pressure
of the reactor is less than 20 bar gauge.
19. The process of claim 1, wherein specific reaction conditions
include a feed rate of the hydrogen stream being in the range of
500 to 5000 standard cubic feet per barrel of feedstock.
20. The process of claim 1, wherein the downstream process is a
para-xylene recovery process.
21. The process of claim 1, further comprising: supplying, to the
reactor, a recycled hydrocarbon stream containing unreacted
alkyl-bridged non-condensed alkyl multi-aromatic compounds.
22. The process of claim 21, wherein the recycled hydrocarbon
stream is combined with the feed stream to form a combined feed
stream being supplied to the reactor.
23. The process of claim 22, wherein the hydrogen stream is
combined with the combined feed stream to form a second combined
stream being supplied to the reactor.
24. The process of claim 1, further comprising: supplying the
product stream to a separation zone to separate the product into a
lighter hydrocarbon stream and a heavier hydrocarbon stream.
25. The process of claim 24, wherein the lighter hydrocarbon stream
is processed to provide a recycled hydrogen stream.
26. The process of claim 25, wherein the recycled hydrogen stream
is combined with a makeup hydrogen stream to provide the hydrogen
stream for supplying to the reactor.
27. The process of claim 1, wherein the downstream process further
comprises: supplying the product stream to a first separator to
provide a first light stream and a first heavy stream; and
supplying the first light stream to a second separator to provide a
second light stream and a second heavy stream; wherein the first
heavy stream and the second heavy stream are combined to form a
heavier hydrocarbon stream.
28. The process of claim 27, wherein the downstream process further
comprises: supplying the heavier hydrocarbon stream to a
fractionation zone for fractionating into two or more streams.
29. The process of claim 27, wherein the downstream process further
comprises supplying the heavier hydrocarbon stream to a first
fractionator for fractionating into a first light fractionation
stream and a first heavy fractionation stream, wherein at least a
portion of the first light fractionation stream is supplied to a
xylene processing unit; and supplying the first heavy fractionation
stream to a second fractionator for fractionating into a second
light fractionation stream and a second heavy fractionation stream,
wherein the second light fractionation stream is supplied to the
xylene processing unit, and at least a portion of the second heavy
fractionation stream is recycled to the reactor.
Description
FIELD
[0001] This disclosure relates to the recovery of light alkylated
mono-aromatics from streams containing alkyl-bridged non-condensed
alkylated multi-aromatic compounds and heavy alkyl-aromatic
compounds during a hydrocarbon refining process.
BACKGROUND
[0002] In an aromatics complex, a variety of process units are used
to convert naphtha or pyrolysis gasoline into benzene, toluene and
mixed xylenes, which are basic petrochemical intermediates used for
the production of various other chemical products. In order to
maximize the production of benzene, toluene and mixed xylenes, the
feed to an aromatics complex is generally limited from C.sub.6 up
to C.sub.11 compounds. In most aromatics complexes, the mixed
xylenes are processed within the complex to produce the particular
isomer--para-xylene, which can be processed downstream to produce
terephthalic acid. This terephthalic acid is used to make
polyesters, such as polyethylene terephthalate. In order to
increase the production of benzene and para-xylene, the toluene and
C.sub.9 and C.sub.10 aromatics are processed within the complex
through a toluene, C.sub.9, C.sub.10 transalkylation/toluene
disproportionation (TA/TDP) process unit to produce benzene and
xylenes. Any remaining toluene, C.sub.9, and C.sub.10 aromatics are
recycled to extinction. Compounds heavier than C.sub.10 are
generally not processed in the TA/TDP unit, as they tend to cause
rapid deactivation of the catalysts used at the higher temperatures
used in these units, often greater than 400.degree. C.
[0003] When para-xylene is recovered from mixed xylenes by a
selective adsorption process unit in the complex, the C.sub.8 feed
to the selective adsorption unit is processed to eliminate olefins
and alkenyl aromatics such as styrene in the feed. Olefinic
material can react and occlude the pores of the zeolite adsorbent.
The olefinic material is removed by passing a C.sub.8+ stream
across a clay or acidic catalyst to react olefins and alkenyl
aromatics with another (typically aromatic) molecule, forming
heavier compounds (C.sub.16+). These heavier compounds are
typically removed from the mixed xylenes by fractionation. The
heavy compounds cannot be processed in the TA/TDP unit due to their
tendency to deactivate the catalyst and are generally removed from
the complex as lower value fuels blend stock.
[0004] Also during hydrocarbon processing, compounds composed of an
aromatic ring with one or more coupled alkyl groups containing
three or more carbon molecules per alkyl group may be formed.
Formation of these compounds may be from processes used by
petroleum refiners and petrochemical producers to produce aromatic
compounds from non-aromatic hydrocarbons, such as catalytic
reforming. As many of these heavy alkyl aromatic compounds
fractionate with the fractions containing greater than 10 carbon
atoms, they are not typically sent as feedstock to the
transalkylation unit, and instead are sent to gasoline blending or
used as fuel oil.
SUMMARY
[0005] A need has been recognized for the characterization and
recovery of higher value light aromatics in the range from C.sub.6
to C.sub.10 from certain heavy compounds before processing aromatic
streams through specialized product production units, such as the
TA/TDP unit. Embodiments disclosed here include characterization of
the products formed during the treatment of aromatics streams
during processing of hydrocarbons. Certain embodiments include
processes for recovery of alkyl mono-aromatic compounds. An example
of one such process includes the steps of supplying, to a reactor,
a feed stream containing one or more of heavy alkyl aromatic
compounds and alkyl-bridged non-condensed alkyl multi-aromatic
compounds; supplying, to the reactor, a hydrogen stream; allowing
the feed stream and the hydrogen stream to react in presence of a
catalyst under specific reaction conditions to produce a product
stream containing one or more alkyl mono-aromatic compounds; and
recovering, from the reactor, the product stream for a downstream
process. The downstream process can be a para-xylene recovery
process. The alkyl-bridged non-condensed alkyl multi-aromatic
compounds include at least two benzene rings connected by an alkyl
bridge group having at least two carbons, wherein the benzene rings
are connected to different carbons of the alkyl bridge group. In
certain embodiments, the feed stream includes C.sub.9+ alkyl
aromatic compounds obtained from a xylene rerun column. The feed
stream can be supplied to the reactor without being diluted by a
solvent.
[0006] In certain embodiments, the hydrogen stream is combined with
the feed stream before being supplied to the reactor. In certain
embodiments, the hydrogen stream includes a recycled hydrogen
stream and a makeup hydrogen stream. In certain embodiments, the
hydrogen stream comprises at least 70% hydrogen by weight. The
catalyst can be presented as a catalyst bed in the reactor. In
certain embodiments, a portion of the hydrogen stream is fed to the
catalyst bed in the reactor to quench the catalyst bed. In certain
embodiments, the catalyst bed is comprised of two or more catalyst
beds. The catalyst can include a support being at least one member
of the group consisting of silica, alumina, and combinations
thereof, and can further include an acidic component being at least
one member of the group consisting of amorphous silica-alumina,
zeolite, and combinations thereof. In certain embodiments, the
catalyst includes an IUPAC Group 8-10 metal and an IUPAC Group 6
metal. In certain embodiments, the catalyst includes an IUPAC Group
8-10 metal being at least one member of the group consisting of
iron, cobalt, and nickel, and combinations thereof and further
includes an IUPAC Group 6 metal being at least one member of the
group consisting of molybdenum and tungsten, and combinations
thereof. In certain embodiments, the IUPAC Group 8-10 metal is 2 to
20 percent by weight of the catalyst and the IUPAC Group 6 metal is
1 to 25 percent by weight of the catalyst. In certain embodiments,
the catalyst is comprised of nickel, molybdenum, ultrastable Y-type
zeolite, and .gamma.-alumina support.
[0007] In certain embodiments, the specific reaction conditions
include an operating temperature of the reactor during the
hydrodearylation reaction being in the range of 200 to 450.degree.
C. The operating temperature of the reactor during the
hydrodearylation reaction can be about 300.degree. C. The operating
temperature of the reactor during the hydrodearylation reaction can
be about 350.degree. C. The specific reaction conditions can
include an hydrogen partial pressure of the reactor during the
hydrodearylation reaction being in the range of 5 to 50 bar gauge.
The hydrogen partial pressure of the reactor during the
hydrodearylation reaction can be maintained at less than 20 bar
gauge. The specific reaction conditions can include a feed rate of
the hydrogen stream being in the range of 500 to 5000 standard
cubic feet per barrel of feedstock.
[0008] Certain embodiments of the process further includes the step
of supplying, to the reactor, a recycled hydrocarbon stream
containing unreacted alkyl-bridged non-condensed alkyl
multi-aromatic compounds. The recycled hydrocarbon stream can be
combined with the feed stream to form a combined feed stream being
supplied to the reactor. The hydrogen stream can be combined with
the combined feed stream to form a second combined stream being
supplied to the reactor. Certain embodiments of the process further
includes the step of supplying the product stream to a separation
zone to separate the product into a lighter hydrocarbon stream and
a heavier hydrocarbon stream. The lighter hydrocarbon stream can be
processed to provide a recycled hydrogen stream. The recycled
hydrogen stream can be combined with a makeup hydrogen stream to
provide the hydrogen stream for supplying to the reactor. Certain
embodiments of the process further includes the steps of: supplying
the product stream to a first separator to provide a first light
stream and a first heavy stream; supplying the first light stream
to a second separator to provide a second light stream and a second
heavy stream. The first heavy stream and the second heavy stream
are combined to form a heavier hydrocarbon stream. Certain
embodiments of the process further includes the step of supplying
the heavier hydrocarbon stream to a fractionation zone for
fractionating into two or more streams. Certain embodiments of the
process further includes the step of supplying the heavier
hydrocarbon stream to a first fractionator for fractionating into a
first light fractionation stream and a first heavy fractionation
stream. Then, at least a portion of the first light fractionation
stream is fed to a xylene complex for further processing, and the
first heavy fractionation stream is supplied to a second
fractionator for fractionating into a second light fractionation
stream and a second heavy fractionation stream. The second light
fractionation stream is supplied to the xylene complex, and at
least a portion of the second heavy fractionation stream is
recycled to the reactor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Embodiments will be readily understood by the following
detailed description in conjunction with the accompanying drawings.
Embodiments are illustrated by way of example and not by way of
limitation in the figures of the accompanying drawings.
[0010] FIG. 1 schematically illustrates a process for the
conversion of alkyl-bridged non-condensed alkyl aromatic compounds
to non-condensed alkyl aromatic compounds, in accordance with
various embodiments.
[0011] FIG. 2 schematically illustrates a system for the conversion
of alkyl-bridged non-condensed alkyl aromatic compounds to
non-condensed alkyl aromatic compounds, in accordance with various
embodiments.
[0012] FIG. 3 is a plot of reactor effluent ASTM D1500 color and
weight fraction boiling at less than 180.degree. C. as a function
of reactor inlet temperature, under reaction conditions described
in Examples.
[0013] FIG. 4 is a plot of reactor effluent density and weight
percentage of mono-aromatics as a function of reactor inlet
temperature, under reaction conditions described in Examples.
DETAILED DESCRIPTION
[0014] The present disclosure describes various embodiments related
to processes, devices, and systems for conversion of alkyl-bridged
non-condensed alkyl aromatic compounds to alkyl mono-aromatic
compounds. Further embodiments are described and disclosed.
[0015] In the following description, numerous details are set forth
in order to provide a thorough understanding of the various
embodiments. In other instances, well-known processes, devices, and
systems may not been described in particular detail in order not to
unnecessarily obscure the various embodiments. Additionally,
illustrations of the various embodiments may omit certain features
or details in order to not obscure the various embodiments.
[0016] In the following detailed description, reference is made to
the accompanying drawings that form a part of this disclosure. The
drawings may provide an illustration of some of the various
embodiments in which the subject matter of the present disclosure
may be practiced. Other embodiments may be utilized, and logical
changes may be made without departing from the scope of this
disclosure. Therefore, the following detailed description is not to
be taken in a limiting sense.
[0017] The description may use the phrases "in some embodiments,"
"in various embodiments," "in an embodiment," or "in embodiments,"
which may each refer to one or more of the same or different
embodiments. Furthermore, the terms "comprising," "including,"
"having," and the like, as used with respect to embodiments of the
present disclosure, are synonymous.
[0018] As used in this disclosure, the term "hydrodearylation"
refers to a process for the cleaving of the alkyl bridge of
non-condensed alkyl-bridged multi-aromatics or heavy alkyl aromatic
compounds to form alkyl mono-aromatics, in the presence a catalyst
and hydrogen.
[0019] As used in this disclosure, the term "stream" (and
variations of this term, such as hydrocarbon stream, feed stream,
product stream, and the like) may include one or more of various
hydrocarbon compounds, such as straight chain, branched or cyclical
alkanes, alkenes, alkadienes, alkynes, alkyl aromatics, alkenyl
aromatics, condensed and non-condensed di-, tri- and
tetra-aromatics, and gases such as hydrogen and methane, C.sub.2+
hydrocarbons and further may include various impurities.
[0020] As used in this disclosure, the term "zone" refers to an
area including one or more equipment, or one or more sub-zones.
Equipment may include one or more reactors or reactor vessels,
heaters, heat exchangers, pipes, pumps, compressors, and
controllers. Additionally, an equipment, such as reactor, dryer, or
vessels, further may include one or more zones.
[0021] As used in this disclosure, the term "rich" means an amount
of at least 50% or greater, by mole percentage of a compound or
class of compounds in a stream. Certain streams rich in a compound
or class of compounds can contain about 70% or greater, by mole
percentage of the particular compound or class of compounds in the
streams. In certain cases, mole percentage may be replaced by
weight percentage, in accordance with standard industry usage.
[0022] As used in this disclosure, the term "substantially" means
an amount of at least 80%, by mole percentage of a compound or
class of compounds in a stream. Certain streams substantially
containing a compound or class of compounds can contain at least
90%, by mole percentage of the compound or class of compounds in
the streams. Certain streams substantially containing a compound or
class of compounds can contain at least 99%, by mole percentage of
the compound or class of compounds in the streams. In certain
cases, mole percentage may be replaced by weight percentage, in
accordance with standard industry usage.
[0023] As used in this disclosure, the term "mixed xylenes" refers
to a mixture containing one or more C.sub.8 aromatics, including
any one of the three isomers of di-methylbenzene and
ethylbenzene.
[0024] As used in this disclosure, the term "conversion" refers to
the conversion of compounds containing multiple aromatic rings or
mono-aromatic compounds with heavy (C.sub.4+) alkyl groups boiling
above 210.degree. C. to mono-aromatic compounds with a lighter
alkyl groups boiling below 210.degree. C.
[0025] The oligomer byproducts formed by the reaction of olefinic
hydrocarbons across an acid catalyst are heavy aromatics and must
be removed by fractionation. The nature of the byproducts formed
has not been well characterized. Embodiments of the disclosure here
include characterization of the C.sub.8+ fraction of reformate. In
certain embodiments, the C.sub.8+ fraction of reformate primarily
contains aromatics (generally more than 95%). The olefinic species
in this fraction are composed primarily of alkenyl aromatics, such
as styrene and methyl-styrene. Such molecules would be expected to
react across clay-containing Lewis-acid sites at temperatures
around 200.degree. C. with the alkyl aromatics via a Friedel-Crafts
reaction to form molecules with two aromatic rings connected with
an alkyl bridge. Alkenyl aromatics may react, in turn, with these
compounds to form multi-aromatic compounds with three or more
aromatic rings connected by alkyl bridges. Such multi-aromatic
compounds may be characterized as having a relatively high density
(greater than 900 kg/m3), a darker brown color (Standard Reference
Method Color greater than 20), and higher boiling points (greater
than 280.degree. C.), as compared to non-bridged alkyl aromatics.
The remaining non-aromatic olefin portion of the C.sub.8+ fraction
of reformate in this embodiment would be expected to react across
clay-containing Lewis acid sites, at temperatures around
200.degree. C., with alkyl aromatics via a Friedel-Crafts reaction
to form mono-aromatic molecules with at least one large (more than
7 carbon atoms) alkyl group. Such heavy mono-aromatics may be
characterized as having a moderately high density (greater than 800
kg/m3), and higher boiling points (greater than 250.degree. C.), as
compared to lighter alkyl aromatics. Such heavy molecules are
separated from C.sub.9 and C.sub.10 mono-aromatics by fractionation
before the C.sub.9 and C.sub.10 aromatics are sent to the TA/TDP
process unit for conversion to benzene and xylenes.
[0026] Processing of a stream containing multi-aromatic compounds
may include separation from lighter unreacted alkyl aromatics by
fractionation, where a separation process may provide at least one
low-boiling point (or light) fraction containing reduced levels of
olefins and at least one high-boiling point (or heavy) fraction
containing the multi-aromatic compounds along with high boiling
point alkyl aromatics. The heavy fraction containing the
multi-aromatic compounds may be utilized as a stream for gasoline
blending because it has a relatively high octane; however, the high
density, darker brown color, and high final boiling point may limit
the amount that may be blended into a gasoline stream.
Alternatively, the heavy fraction containing the multi-aromatic
compounds may be utilized as a fuel oil blend component. The heavy
fraction containing the multi-aromatics typically is not processed
in catalytic units such as a toluene/C.sub.9/C.sub.10
transalkylation unit, because the condensed multi-aromatics in the
heaviest fractions with greater than ten carbon atoms tend to form
catalyst-deactivating coke layers at the conditions used in such
units. The formation of coke layers potentially limits catalyst
life between regenerations. Accordingly, alternative processing
methods and systems are needed to optimize the use of a hydrocarbon
process stream containing alkyl-bridged non-condensed alkyl
aromatic compounds.
[0027] Certain embodiments disclosed here relate to recovery of
light alkylated mono-aromatics from streams containing
alkyl-bridged non-condensed alkylated multi-aromatic compounds and
heavy alkyl-aromatic compounds during a hydrocarbon refining
process. Alkyl-bridged non-condensed alkyl aromatic compounds may
be referred to as multi-aromatics or poly-aromatics. Conversion of
multi-aromatics into alkyl mono-aromatics may be desirable to
optimize the use of hydrocarbon process streams containing
multi-aromatics. In various embodiments, recovery processes provide
alkyl mono-aromatic compounds that have retained the high octane
properties of the multi-aromatics. Retaining a high octane may be
desirable for gasoline blending of the alkyl aromatics. In various
embodiments, the density, color, and boiling point properties may
be improved by the recovery processes, resulting in a higher value
hydrocarbon stream for blending into gasoline streams. In various
embodiments, the processes for conversion of multi-aromatics into
alkyl aromatics may allow for the use of the alkyl aromatics as
feedstock to a benzene, toluene, ethylbenzene, and xylenes (BTEX)
petrochemicals processing unit. In various embodiments, the
processes for conversion of multi-aromatics into alkyl aromatics
may allow for the use of the alkyl aromatics as feedstock within a
TA/TDP unit. Accordingly, certain embodiments may provide higher
value use of a hydrocarbon stream containing multi-aromatics by
converting these compounds to alkyl aromatics.
[0028] Certain embodiments disclosed here relate to methods for
recovery of light alkylated mono-aromatics from streams containing
alkyl-bridged non-condensed alkylated multi-aromatic compounds and
heavy alkyl-aromatic compounds. One such method includes the steps
of supplying to a reactor a feed stream containing a plurality of
alkyl bridged non-condensed alkyl aromatic compounds and heavy
alkyl aromatic compounds; supplying a hydrogen stream to the
reactor; allowing the feed stream and the hydrogen stream to react
in the presence of a catalyst to produce a product stream
containing alkyl mono-aromatic compounds; and recovering, from the
reactor, the product stream. The alkyl-bridged non-condensed alkyl
aromatic compounds include at least two benzene rings connected by
an alkyl bridge group having at least two carbons, wherein the
benzene rings are connected to at least two different carbons of
the alkyl bridge group. The feed stream can be a C.sub.9+ heavy
aromatics stream from a xylenes rerun column. The feed stream can
be a C.sub.9+ aromatics stream, which includes di, tri, and poly
aromatics (C.sub.9 to C.sub.16+). In certain embodiments, the feed
stream may be diluted by a solvent or may be supplied without any
dilution by a solvent. In certain embodiments, the feed stream is
combined with the hydrogen stream and supplied as a combined stream
to the reactor. In certain embodiments, the hydrogen stream
includes a combination of a recycled hydrogen stream and a makeup
hydrogen stream. The hydrogen stream can contain at least 70%
hydrogen by weight. The catalyst may be provided as a catalyst bed
in the reactor. In certain embodiments, a portion of the hydrogen
stream is fed to the catalyst bed of the reactor to quench the
catalyst bed. The catalyst bed may include two or more catalyst
beds. In certain embodiments, the catalyst includes a support
selected from the group consisting of silica and alumina, and
combinations thereof, and further includes an acidic component
selected from the group consisting of amorphous silica-alumina and
zeolite, and combinations thereof. The catalyst can include an
IUPAC Group 8-10 metal and an IUPAC Group 6 metal. The catalyst can
include an IUPAC Group 8-10 metal selected from the group
consisting of iron, cobalt, and nickel, and combinations thereof,
and further includes an IUPAC Group 6 metal selected from the group
consisting of molybdenum and tungsten, and combinations thereof.
Certain catalysts used here contain the IUPAC Group 8-10 metal as 2
to 20 percent by weight of the catalyst and the IUPAC Group 6 metal
as 1 to 25 percent by weight of the catalyst. The catalyst can
include one or more of nickel, molybdenum, ultrastable Y-type
zeolite, and .gamma.-alumina support. The reactor is operated under
suitable temperature and pressure conditions for optimal recovery
of the alkylated mono-aromatics. Such operating conditions can
include maintaining the temperature of the reactor between 200 to
450.degree. C. during the hydrodearylation reaction. Such operating
conditions can include maintaining the temperature of the reactor
around 300.degree. C. to 350.degree. C. during the hydrodearylation
reaction. The hydrogen partial pressure of the reactor can range
from 5 to 50 bar gauge. The hydrogen partial pressure of the
reactor can be maintained at less than 20 bar gauge. The feed rate
of the hydrogen stream can be 500 to 5000 standard cubic feet per
barrel of the hydrocarbon feed stream. Operating conditions can
include a liquid hourly space velocity of the reactor of about 0.5
to 10 per hour.
[0029] Certain embodiments of the method can also include the step
of supplying, to the reactor, a recycled hydrocarbon stream
including a plurality of unreacted alkyl bridged non-condensed
alkyl aromatic compounds. In certain embodiments, the recycled
hydrocarbon stream is combined with the feed stream and supplied to
the reactor as a single stream. In certain embodiments, the
hydrogen stream can be combined with the combined feed stream of
the recycled hydrocarbon stream and the feed stream and supplied to
the reactor as a single stream. Certain embodiments can include
supplying the product stream to a separation zone to separate the
product into a lighter hydrocarbon stream and a heavier hydrocarbon
stream. In certain embodiments, the product stream includes C.sub.8
to C.sub.10 range alkyl mono-aromatics. In certain embodiments, the
majority of the olefins obtained from the heavy reformate clay
treaters (C8+) are primarily alkenyl aromatics, and they will react
with alkyl aromatics to form the uncondensed alkyl multi-aromatics.
The uncondensed alkyl multi-aromatics are hydrodearylated at
relatively low temperature and pressure in these certain
embodiments, allowing for the conversion to alkyl mono-aromatics
while avoiding the excessive catalyst deactivation expected at
higher temperatures with a heavy stream. Certain embodiments can
include supplying the product stream to a para-xylene recovery
process.
[0030] FIG. 1 schematically illustrates a process 100 for the
recovery of light alkylated mono-aromatics from streams containing
alkyl-bridged non-condensed alkylated multi-aromatic compounds and
heavy alkyl-aromatic compounds, in accordance with various
embodiments. The step 102 of process 100 includes supplying, to a
reactor, a hydrocarbon feedstock including a plurality of alkyl
bridged non-condensed alkyl multi-aromatic compounds. In various
embodiments, the alkyl bridged non-condensed alkyl aromatic
compounds include at least two benzene rings connected by an alkyl
bridge group having at least two carbons, where the benzene rings
are connected to different carbons of the alkyl bridge group. In
various embodiments, the alkyl bridged non-condensed alkyl aromatic
compounds include additional alkyl groups connected to the benzene
rings of the alkyl bridged non-condensed alkyl aromatic compounds.
The hydrocarbon feedstock can be a stream in a petroleum refinery
from one or more hydrocarbons treatments. In various embodiments,
the hydrocarbon feedstock may comprise a heavy aromatics stream
from a unit operation of a petroleum refinery. In various
embodiments, the hydrocarbon feedstock may comprise a C.sub.9+
heavy aromatics stream from a xylene rerun column of a petroleum
refinery. In various embodiments, the hydrocarbon feedstock is
undiluted by a solvent.
[0031] By way of example and not limitation, the various alkyl
bridged non-condensed alkyl aromatic compounds may include a
mixture of chemical compounds illustrated by Formula I, Formula II,
and Formula III, and various combinations of these compounds.
##STR00001##
R.sub.2, R.sub.4, and R.sub.6 are alkyl bridge groups independently
having from two to six carbon atoms. R.sub.1, R.sub.3, R.sub.5, and
R.sub.7 are independently selected from the group consisting of
hydrogen and an alkyl group having from one to eight carbon atoms.
In addition to the groups R.sub.1, R.sub.3, R.sub.5, and R.sub.7,
the benzene groups of Formulas I, II, and III may further include
additional alkyl groups connected to the benzene groups,
respectively. In addition to the four benzene groups of Formula
III, the various alkyl bridged non-condensed alkyl aromatic
compounds may include five or more benzene groups connected by
alkyl bridges, where the additional benzene groups further may
include alkyl groups connected to the additional benzene
groups.
[0032] The step 104 of process 100 includes supplying, to the
reactor, a hydrogen stream. In various embodiments, the hydrogen
stream may be combined with the hydrocarbon feedstock to form a
combined feedstock stream that is subsequently fed to the reactor.
In various embodiments, the hydrogen stream may include a recycled
hydrogen stream and a makeup hydrogen stream. In various
embodiments, the recycled hydrogen stream may be a stream from
processing of a hydrocarbon product stream from the reactor. In
various embodiments, the hydrogen stream may contain at least 70
mole percent hydrogen. In various embodiments, the hydrogen stream
may contain at least 80 mole percent hydrogen. In various
embodiments, the hydrogen stream may contain at least 90 mole
percent hydrogen.
[0033] The step 106 of process 100 includes allowing a
hydrodearylation reaction to occur in the presence of a catalyst
under suitable reaction conditions, such that the alkyl bridges of
the alkyl bridged non-condensed alkyl multi-aromatic compounds and
heavy alkyl aromatic compounds are cleaved to produce alkyl
mono-aromatic compounds. In various embodiments, non-bridging alkyl
groups connected to the benzene rings of the alkyl bridged
non-condensed alkyl aromatic compounds remain connected to the
benzene rings of the non-condensed alkyl aromatic compounds in the
hydrocarbon product. By way of example and not limitation, the
various alkyl mono-aromatic compounds may include a mixture of
chemical compounds illustrated by Formula IV.
##STR00002##
For the various alkyl mono-aromatic compounds, R.sub.1 is
independently selected from the group consisting of an alkyl group
having from one to eight carbon atoms, and R.sub.2 is independently
selected from the group consisting of hydrogen and an alkyl group
having from one to eight carbon atoms.
[0034] In various embodiments, an operating temperature of the
reactor may be 200 to 450.degree. C., within reasonable engineering
tolerances, during the cleaving of the alkyl bridges. In various
embodiments, the operating temperature for the reactor may be
approximately 300.degree. C., within reasonable engineering
tolerances, for the cleaving of the alkyl bridges. In various
embodiments, the operating temperature for the reactor may be
350.degree. C., within reasonable engineering tolerances, for the
cleaving of the alkyl bridges. In various embodiments, an hydrogen
partial pressure of the reactor may be 5 to 50 bar gauge, within
reasonable engineering tolerances. In various embodiments, the
hydrogen partial pressure for the reactor may be less than 20 bar
gauge, within reasonable engineering tolerances. In various
embodiments, a feed rate of the hydrogen stream may be 500 to 5000
standard cubic feet per barrel of feedstock, within reasonable
engineering tolerances. In various embodiments, a liquid hourly
space velocity of the reactor may be 0.5 to 10 per hour, within
reasonable engineering tolerances.
[0035] The step 108 of process 100 includes recovering, from the
reactor, a hydrocarbon product containing the alkyl mono-aromatic
compounds. In various embodiments, the hydrocarbon product may be
an effluent stream from the reactor. In various embodiments, the
effluent stream may be fed to various separation processes to
recover unreacted hydrogen, the alkyl mono-aromatic compounds, and
the unreacted alkyl-bridged non-condensed alkyl aromatic compounds.
In various embodiments, the recovered unreacted hydrogen may be
recycled back to the reactor. In various embodiments, the unreacted
alkyl-bridged non-condensed alkyl aromatic compounds may be
partially recycled back to the reactor. In various embodiments, the
alkyl mono-aromatic compounds may be further processed to recovery
various high value hydrocarbons.
[0036] The step 110 of process 100 includes supplying, to the
reactor, a recycled hydrocarbon stream including a plurality of
unreacted alkyl bridged non-condensed alkyl aromatic compounds. In
various embodiments, the recycled hydrocarbon stream may be a
stream from processing of a hydrocarbon product from the reactor.
In various embodiments, the recycled hydrocarbon stream may be
combined with the feedstock stream to form a combined feedstock
stream that is fed to the reactor. In various embodiments, the
hydrogen stream may be combined with the combined feed stream to
form a second combined stream that is fed to the reactor. In
various embodiments, the recycled hydrocarbon stream, the hydrogen
stream, and the feedstock stream may be combined in any order to
form a combined stream that is fed to the reactor. In various
embodiments, the recycled hydrocarbon stream, the hydrogen stream,
and the feedstock stream may be fed separately to the reactor or
two of the streams may be combined and the other fed separately to
the reactor. In various embodiments, the hydrogen stream has a
portion of the stream fed directly to one or more catalyst beds of
the reactor.
[0037] The step 112 of process 100 includes supplying, the
hydrocarbon product to a separation zone to separate the
hydrocarbon product into a lighter hydrocarbon stream and a heavier
hydrocarbon stream. In various embodiments, the separation zone may
comprise a first separator and a second separator. The hydrocarbon
product may be fed to the first separator to provide a first light
stream and a first heavy stream from the first separator. The first
light stream may be fed to the second separator to provide a second
light stream and a second heavy stream. The first heavy stream and
the second heavy stream may be combined to form the heavier
hydrocarbon stream. The second light stream may be the lighter
hydrocarbon stream from the separation zone. In various
embodiments, the lighter hydrocarbon stream may be processed to
provide a recycled hydrogen stream. In various embodiments, the
recycled hydrogen stream may be combined with a makeup hydrogen
stream to provide the hydrogen stream to be supplied to the
reactor.
[0038] The step 114 of process 100 includes supplying the heavier
hydrocarbon stream to a fractionation zone for fractionating into
two or more streams. In various embodiments, the fractionation zone
may comprise a first fractionator and a second fractionator. The
heavier hydrocarbon stream may be fed to the first fractionator for
fractionating into a first light fractionation stream and a first
heavy fractionation stream. At least a portion of the first light
fractionation stream may be fed to a xylene complex for processing
to recover xylenes. The first heavy fractionation stream may be fed
to the second fractionator for fractionating into a second light
fractionation stream and a second heavy fractionation stream. The
second light fractionation stream may be fed to the xylene complex
for recovery of xylenes. In various embodiments, a portion of the
second heavy fractionation stream may be recycled to the reactor to
provide the recycled hydrocarbon stream. In various embodiments, a
portion of the second heavy fractionation stream may be a bleed
stream to prevent buildup of the alkyl-bridged non-condensed alkyl
aromatic compounds in the various process flow streams. A flow rate
of the bleed stream may be adjusted accordingly to ensure no heavy
aromatic hydrocarbon build up in the various process flow
streams.
[0039] FIG. 2 schematically illustrates a system 200 for the
conversion of alkyl-bridged non-condensed alkyl aromatic compounds
to alkyl mono-aromatic compounds, in accordance with various
embodiments. The system 200 may be referred to as a single stage
hydrodearylation system for the conversion of heavy aromatics to
non-condensed alkyl aromatics. The various process flow lines
illustrated in FIG. 2 may be referred to as streams, feeds,
products, or effluents. Additionally, not all heat transfer, mass
transfer, and fluid conveying equipment are illustrated, and the
requirements for these items are well understood by a person of
ordinary skill in the art.
[0040] The system 200 may include a hydrodearylation reaction zone
202. The reaction zone 202 may include a reactor 204. The reactor
204 may include an effective quantity of a suitable catalyst. The
catalyst may be in a catalyst bed. The reactor 204 may include an
inlet for receiving a combined stream 210 including a feedstock
stream 206, a recycle stream 208, and a hydrogen stream 212. The
feedstock stream 206 may be a stream including C.sub.9+ aromatics.
A hydrodearylated effluent stream 214 may be discharged from an
outlet of reactor 204. The hydrodearylation reactor 204 may have a
single or multiple catalyst beds and may receive quench hydrogen
stream in between the beds of a multi-bed arrangement. Although not
shown, the quench hydrogen stream may be a portion of the hydrogen
stream 212 piped to the various locations of the catalyst beds in
the reactor 204.
[0041] In various embodiments, the degree of conversion in the
hydrodearylation zone 202 may be kept below a threshold to limit
the amount of catalyst required and the amount of coking on the
catalyst. By way of example and not limitation, a threshold limit
may be 70% of a maximum potential conversion in the reactor 204.
The hydrodearylated effluent stream 214 may pass to a separation
zone 230. The separation zone may include two separators, a hot
separator 232 and the cold separator 234. The hot separator 232 may
include an inlet for receiving the reactor effluent 214, an outlet
for discharging a hydrodearylated gas stream 236, and an outlet for
discharging a hydrodearylated liquid stream 240. The cold separator
234 may include an inlet for partially condensed hydrodearylated
gas stream 236, an outlet for discharging a vapor stream 238 and
outlet for discharging a hydrocarbon liquid stream 242. Heat
exchangers may be included to cool the hot stream 236 before
entering subsequent cold separator 234. The heat exchangers are not
shown and any design requirements for the heat exchangers are well
understood by a person having ordinary skill in the art. The stream
236 may include one or more gases selected from a group consisting
of hydrogen, methane, ethane, C.sub.3+ hydrocarbons, and
combinations thereof. The stream 236 may exit the hot separator 232
and be fed to the cold separator 234.
[0042] The vapor stream 238 from cold separator 234 may be rich in
hydrogen. The vapor stream 238 may be recycled back after
compression through recycling system 270 with a compressor 272 to
produce a stream 274. The stream 274 may be combined with a
hydrogen make up stream 276. The hydrogen makeup stream 276 may be
a high purity make up gas containing substantially hydrogen from a
header. The combined stream may be recycled back to the feed
section through the header to provide the hydrogen stream 212.
[0043] The liquid stream 242 from the cold separator 234 may be
preheated in a heat exchanger train (not shown). The liquid stream
242 may be combined with the hot hydrocarbon liquid stream 240 to
form a liquid stream 244, which may flow to a fractionation zone
250.
[0044] The fractionation zone 250 may include a stripper column 252
and a splitter column 254. The columns 252, 254 may be reboiled
fractionation columns. The liquid stream 244 may enter the stripper
column 252. The stripper column 252 may be a trayed column or a
packed column, or a combination of the two types of columns. The
stripper column 252 may form two streams, a light vapor stream 256
and a bottom stream 260. The vapor stream 256 may be condensed, and
a portion may be a liquid reflux for the stripper column 252. A
portion of the condensed and non-condensed vapor stream 256 may be
routed for further processing. By way of example and not
limitation, the condensed and non-condensed vapor stream 256 may be
processed in a reformate splitter column or a heavy aromatics
column within a para-xylene aromatic complex. These details of
further processing are not shown in FIG. 2 as they are understood
by a person of ordinary skill in the art.
[0045] The bottom stream 260 from stripper column 252 may be routed
into the splitter column 254. The splitter column 254 may be a
trayed column or a packed column, or a combination of the two types
of columns. The splitter column 254 may form two streams, a light
stream 258 and a heavy stream 262. The light stream 258 may be
comprised of C.sub.6+ compounds. The heavy stream 262 may be
comprised of C.sub.10+ compounds.
[0046] The light stream 258 may be condensed and portion of the
condensed light stream may be a liquid refluxed to the splitter
column 254. A portion of the light stream 258 that is not refluxed
to the splitter column 254 may be routed for further processing. By
way of example, this portion of the light stream 258 may be routed
to a reforming/para-xylene complex for xylene recovery. The heavy
stream 262 may be split into two streams, a recycle stream 208 and
a bleed stream 264. A flow rate of the bleed stream 264 may be
adjusted accordingly to ensure no heavy aromatic hydrocarbon build
up in the reaction stream 210.
[0047] In various embodiments, the hydrogen stream 212 may be a
once-through stream without recycling via streams 238, 274.
Accordingly, a hydrogen stream 276 may be added via a manifold to
form hydrogen stream 212 without stream 274. In various
embodiments, flashed gases from the cold separator 234 may be
routed out of the system 200 and back to a hydrogen generation
source (not shown). In various embodiments, when the hydrogen
stream 212 is a once-through stream, the separator effluent liquid
244 may be directly routed to a xylene rerun column within a
para-xylene complex.
[0048] In various embodiments, the hydrodearylation reaction zone
202 may include two reactors in parallel and may be used with an
in-situ regeneration loop. As a fixed bed catalyst system is
susceptible to coking when processing heavy aromatics, one reactor
may be operating while the other reactor is in a regeneration mode
for various embodiments.
[0049] In various embodiments, the hot and cold separators 232, 234
may be replaced by a single separator with a heat exchanger train
to preheat the hydrogen stream 212 or the combined stream 210 with
reactor effluent 214.
[0050] In various embodiments, the feedstock stream 206 may be a
heavy hydrocarbons stream. The heavy hydrocarbons stream may be
C.sub.9+ or C.sub.10+ from a xylene rerun column or a heavy
aromatic column bottoms from a para-xylene aromatic complex. The
feedstock stream 206 may include C.sub.9 to C.sub.16+, and this
stream may be predominantly mono-aromatics, di-aromatics, and
poly-aromatics.
[0051] In various embodiments, the hydrodearylation reaction zone
202 may include a reactor 204 having a single catalyst bed or
multiple catalyst beds. In various embodiments, the multiple
catalyst beds may receive quench a hydrogen stream between the
beds. Although not illustrated in FIG. 2, the hydrogen stream 212
may be provided anywhere along the reactor 204, and multiple
hydrogen streams may be provided, depending upon the number of
beds.
[0052] In various embodiments, the reactor 204 may contain a
catalyst having at least one IUPAC Group 8-10 metal, and at least
one IUPAC Group 6 metal. The IUPAC Group 8-10 metal may be selected
from the group consisting of iron, cobalt, and nickel, and
combinations thereof. The IUPAC Group 6 metal may be selected from
a group consisting of molybdenum and tungsten, and combinations
thereof. The IUPAC Group 8-10 metal may be present in an amount of
approximately 2-20% by weight, and the IUPAC Group 6 metal may be
present in an amount of approximately 1-25% by weight. In various
embodiments, the IUPAC Group 8-10 and IUPAC Group 6 metals may be
on a support material. In various embodiments, the support material
may be silica or alumina, and may further include an acidic
component selected from the group consisting of an amorphous silica
alumina, a zeolite or a combination of the two. In various
embodiments, the reactor 204 may contain a catalyst having any
noble IUPAC Group 8-10 metal on a silica-alumina or alumina support
having an acid cracking component of an amorphous silica-alumina or
a zeolite, or a combination of the two. In certain embodiments, the
reactor 204 may contain a catalyst selected from the group
consisting of platinum, palladium, and combinations thereof, on a
silica-alumina or alumina support having an acid cracking component
of an amorphous silica-alumina or a zeolite, or a combination of
the two.
[0053] In various embodiments, operating conditions for the
hydrodearylation reaction zone 202 may include a reaction
temperature in the range of from 200.degree. C. to 450.degree. C.
(392.degree. F. to 840.degree. F.), and a hydrogen partial pressure
in the range of from 5 bar gauge to 50 bar gauge (70 psig to 725
psig). In various embodiments, operating conditions for the hot
separator 232 may include a temperature in the range of from
200.degree. C. to 400.degree. C. (392.degree. F. to 750.degree.
F.), and a hydrogen partial pressure in the range of from 5 bar
gauge to 50 bar gauge (70 psig to 725 psig). In various
embodiments, operating conditions for the cold separator 234 may
include a temperature in the range of from 40.degree. C. to
80.degree. C. (104.degree. F. to 176.degree. F.), and a pressure in
the range of from 5 bar gauge to 50 bar gauge (70 psig to 725
psig). In various embodiments, operating conditions for the
fractionation zone 250 may include a temperature in the range of
from 40.degree. C. to 300.degree. C. (104.degree. F. to 572.degree.
F.), and a pressure in the range of from 0.05 bar to 30 bar (0.73
psig to 435 psig).
Examples
[0054] According to various embodiments, the present disclosure
describes methods and systems for a hydrodearylation, as
illustrated and described for the various embodiments. In an
example of a hydrodearylation process, a feedstock consisting of a
xylenes rerun column bottoms stream with an ASTM D1500 color of 5,
a density of 0.9125 g/cm.sup.3, and a 57 weight percent of
hydrocarbons boiling below 180.degree. C. (356.degree. F.) was
reacted in a hydrodearylation reaction zone containing a catalyst
having nickel and molybdenum with ultrastable Y-type (USY) zeolite
on a silica-alumina support operated at hydrodearylation conditions
including a temperatures from 200 to 450.degree. C. (392 to
842.degree. F.), at a hydrogen partial pressure of 15 bara (218
psia), a liquid hourly space velocity of 1.3 hr.sup.-1. The results
of the hydrodearylation reactions are summarized in FIGS. 3 and
4.
[0055] FIG. 3 is a plot of reactor effluent ASTM D1500 color and
weight fraction boiling at less than 180.degree. C. as a function
of reactor inlet temperature. As can be seen in FIG. 3, a
temperature of approximately 350.degree. C. appears to provide a
higher percentage of lower boiling fraction and a lower color value
as compared to other inlet reactor temperatures. FIG. 4 is a plot
of reactor effluent density and weight percentage of mono-aromatics
as a function of reactor inlet temperature. As can be seen in FIG.
4, a reactor inlet temperature between 350.degree. C. and
400.degree. C. appears to provide a higher percentage of
mono-aromatics under these reaction conditions and a lower density
as compared to other inlet reactor temperatures.
[0056] Ranges may be expressed herein as from about one particular
value and to about another particular value. When such a range is
expressed, it is to be understood that another embodiment is from
the one particular value and/or to the other particular value,
along with all combinations within said range. Where the range of
values is described or referenced herein, the interval encompasses
each intervening value between the upper limit and the lower limit
as well as the upper limit and the lower limit and includes smaller
ranges of the interval subject to any specific exclusion
provided.
[0057] Where a method comprising two or more defined steps is
recited or referenced herein, the defined steps can be carried out
in any order or simultaneously except where the context excludes
that possibility.
[0058] While various embodiments have been described in detail for
the purpose of illustration, they are not to be construed as
limiting, but are intended to cover all the changes and
modifications within the spirit and scope thereof.
* * * * *