U.S. patent application number 12/976295 was filed with the patent office on 2012-06-28 for high purity heavy normal paraffins utilizing integrated systems.
This patent application is currently assigned to UOP LLC. Invention is credited to Andrea G. Bozzano, Jeffrey L. Pieper, Stephen W. Sohn.
Application Number | 20120160742 12/976295 |
Document ID | / |
Family ID | 46314738 |
Filed Date | 2012-06-28 |
United States Patent
Application |
20120160742 |
Kind Code |
A1 |
Sohn; Stephen W. ; et
al. |
June 28, 2012 |
High Purity Heavy Normal Paraffins Utilizing Integrated Systems
Abstract
A process is presented for producing a purified normal paraffin
product stream. The process includes passing a hydrocarbon stream
having the desired normal paraffins to an adsorption separation
system. A process stream generated from the separation system and
having the normal paraffins is passed to an adsorption unit for the
selective adsorption of aromatic compounds from the process stream,
thereby producing a purified product.
Inventors: |
Sohn; Stephen W.; (Arlington
Heights, IL) ; Bozzano; Andrea G.; (Northbrook,
IL) ; Pieper; Jeffrey L.; (Des Plaines, IL) |
Assignee: |
UOP LLC
Des Plaines
IL
|
Family ID: |
46314738 |
Appl. No.: |
12/976295 |
Filed: |
December 22, 2010 |
Current U.S.
Class: |
208/264 |
Current CPC
Class: |
C10G 45/02 20130101;
C10G 67/14 20130101; C10G 2400/30 20130101; C10G 45/44 20130101;
C10G 67/06 20130101; C10G 2300/201 20130101; C10G 25/08 20130101;
C10G 25/12 20130101; C10G 7/00 20130101 |
Class at
Publication: |
208/264 |
International
Class: |
C10G 45/00 20060101
C10G045/00 |
Claims
1. A process for producing a purified heavy normal paraffin,
comprising: passing a hydrocarbon feedstream to a prefractionation
unit, thereby generating a first stream comprising light ends, a
second stream comprising heavy ends, and a third stream comprising
the selected hydrocarbons; passing the third stream to a
hydroprocessing unit, thereby creating a effluent stream having
reduced contaminants; passing the effluent stream to an adsorption
separation unit, thereby creating an extract stream comprising
normal paraffins, and a raffinate stream comprising non-normal
hydrocarbons and desorbent; and passing the extract stream to an
aromatics adsorbent unit for selective adsorption of aromatics,
thereby creating a process extract stream having heavy aromatic
content of less than 0.5 wt %.
2. The process of claim 1 wherein the heavy aromatic content
comprises aromatics in the C14 to C17 range.
3. The process of claim 1 further comprising the process extract
stream to a separation unit, thereby creating the purified heavy
normal paraffin stream, and a light aromatics stream.
4. The process of claim 3 wherein the light aromatics stream
comprises C6 to C8 aromatics.
5. The process of claim 4 wherein the light aromatics stream
comprises para-xylene.
6. The process of claim 1 further comprising regeneration of the
aromatics adsorbent unit.
7. The process of claim 6 wherein the regeneration comprises:
purging the adsorbent unit, thereby creating a purge stream; and
passing a desorbent through the adsorbent unit, thereby creating a
desorption stream.
8. The process of claim 7 wherein the adsorbent unit is purged with
a purge stream comprising light hydrocarbons in the C5 to C10
range.
9. The process of claim 8 wherein the purge stream comprises
mixture of pentane and isooctane.
10. The process of claim 7 wherein the adsorbent unit is treated
with paraxylene desorbent.
11. The process of claim 7 wherein the purge stream and the
desorption stream are passed to a separation unit, thereby creating
a first stream comprising the purge stream, a second stream
comprising the desorbent, and a third stream comprising aromatics
in the C14 to C17 range.
12. The process of claim 1 wherein the hydroprocessing unit also
performs partial hydrogenation of aromatics.
13. The process of claim 1 wherein the heavy aromatic content in
the process extract stream is less than 100 ppmw.
14. The process of claim 1 wherein the selected hydrocarbons are
C14 to C17 hydrocarbons.
15. A process for producing a purified heavy normal paraffin,
comprising: passing a hydrocarbon feedstream to a prefractionation
unit, thereby generating a first stream comprising light ends
comprising hydrocarbons having 13 or less carbon atoms, a second
stream comprising heavy ends comprising hydrocarbons having 18 or
more carbon atoms, and a third stream comprising the selected
hydrocarbons having from 14 to 17 carbon atoms; passing the third
stream to a hydroprocessing unit, thereby creating a effluent
stream having reduced contaminants, and partially hydrogenating
aromatics; passing the effluent stream to an adsorption separation
unit, thereby creating an extract stream comprising normal
paraffins, and a raffinate stream comprising non-normal
hydrocarbons; passing the extract stream to an on-line aromatics
adsorbent unit for selective adsorption of aromatics in the C14 to
C17 range, thereby creating a process extract stream having an
aromatic content in the C14 to C17 range of less than 0.5 wt %; and
passing the extract stream to an extract separation unit, thereby
creating a purified heavy normal paraffin stream, and an overhead
stream.
16. The process of claim 15 wherein the overhead stream from the
extract separation unit comprises a desorption hydrocarbon used to
remove adsorbed aromatics from the adsorption unit.
17. The process of claim 16 wherein the desorption hydrocarbon
comprises para-xylene.
18. The process of claim 15 wherein the regeneration comprises:
taking the aromatics adsorbent unit off-line; purging the off-line
adsorbent unit, thereby creating a purge stream; and passing a
desorbent through the adsorbent unit, thereby creating a desorption
stream.
19. The process of claim 18 wherein the purge stream and the
desorption stream are passed to a separation unit, thereby creating
a first stream comprising the purge material, a second stream
comprising the desorbent, and a third stream comprising aromatics
in the C14 to C17 range.
20. The process of claim 15 wherein the process utilizes at least
two aromatics adsorbent units, and at least one adsorbent unit is
off-line, further comprising: taking the on-line aromatics
adsorbent unit off-line for regeneration; and putting the off-line
aromatics adsorbent unit on-line.
Description
FIELD OF THE INVENTION
[0001] The invention relates to adsorption separation processes.
The invention is specifically directed at a process to improve the
capacity and purity of normal paraffins.
BACKGROUND OF THE INVENTION
[0002] The separation of various substances through selective
adsorption is an important process for producing pure substances.
However, this generally is a batch process, but with the
development of simulated moving bed (SMB) technology, the
adsorption separation process can be operated on a continuous
basis. For simulated moving bed technology, the process uses a
multiport rotary valve to redirect flow lines in the process. The
simulation of a moving adsorbent bed is described in U.S. Pat. No.
2,985,589 (Broughton et al.). In accomplishing this simulation, it
is necessary to connect a feed stream to a series of beds in
sequence, first to bed no. 1, then to bed no. 2, and so forth for
numerous beds, the number of beds often being between 12 and 24.
These beds may be considered to be portions of a single large bed
whose movement is simulated. Each time the feed stream destination
is changed, it is also necessary to change the destinations (or
origins) of at least three other streams, which may be streams
entering the beds, such as the feed stream, or leaving the beds.
The moving bed simulation may be simply described as dividing the
bed into series of fixed beds and moving the points of introducing
and withdrawing liquid streams past the series of fixed beds
instead of moving the beds past the introduction and withdrawal
points. A rotary valve used in the Broughton process may be
described as accomplishing the simultaneous interconnection of two
separate groups of conduits.
[0003] There are many different process requirements in moving bed
simulation processes, resulting in different flow schemes and thus
variations in rotary valve arrangement. For example, in addition to
the four basic streams described in Broughton (U.S. Pat. No.
2,985,589), it may be desirable to utilize one or more streams to
purge, or flush, a pipeline or pipelines. A flush stream is used to
prevent undesirable mixing of components. The flush substance is
chosen to be one which is not undesirable for mixing with either
main stream, that being purged or that which enters the pipeline
after flushing is completed. U.S. Pat. No. 3,201,491 (Stine et al.)
may be consulted for information on flushing lines as applied to
the process of Broughton (U.S. Pat. No. 2,985,589). It may be
desirable to pass fluid through a bed or beds in the reverse
direction from normal flow. This is commonly known as backflushing,
a subject treated in US (Fickel). Other applications for various
arrangements of multiport rotary disc valves may be seen in U.S.
Pat. No. 4,313,015 (Broughton); U.S. Pat. No. 4,157,267 (Odawara et
al.); U.S. Pat. No. 4,182,633 (Ishikawa et al.); and U.S. Pat. No.
4,409,033 (LeRoy).
[0004] While the multiport rotary disc valve of Carson (U.S. Pat.
No. 3,040,777) provided a satisfactory valve design for the
simultaneous interconnection of two independent groups of conduits
such that each conduit of the first group could be brought into
individual communication with every conduit of the second group, it
is not suitable when three groups of conduits must be
simultaneously interconnected in the same manner. Upon reference to
Broughton (U.S. Pat. No. 2,985,589), it can be seen that there are
only two groups of conduits which need to be interconnected when
the arrangement of the drawing of that patent is utilized. One
group consists of the conduits which provide the flows entering and
leaving the simulated moving bed adsorbent system, that is, the
flows which are switched among the beds, such as the feed stream. A
second group consists of the conduits associated with the
individual beds, that is, which supply and remove fluid from the
beds, one conduit being connected between each two beds. It is to
be noted that each conduit of the second group serves that dual
function of supply and removal, so that it is unnecessary to
provide conduits for supplying fluid separate from those for
removing fluid.
[0005] Adsorption separation uses expensive equipment, and the
equipment is not readily replaced to increase the production of a
product stream. With increasing demand for the products from
adsorption separation processes, increasing the throughput and
recovery of the products is desirable without having to replace the
equipment.
SUMMARY OF THE INVENTION
[0006] The present invention improves the purity of a normal
paraffin stream by selectively removing aromatic compounds from the
extract stream. The process is for the production of a purified
heavy normal paraffin. A hydrocarbon stream is passed to a
prefractionation unit to separate out a selected range of
hydrocarbons. The prefractionation unit generates a first stream
comprising light ends, a second stream comprising heavy ends, and a
third stream comprising hydrocarbons in the desired range. The
third stream is passed to a hydroprocessing unit where under a
hydrogen atmosphere, contaminants within the stream are
hydrogenated and removed, creating an effluent stream having
reduced contaminants. The effluent stream is processed in an
adsorption separation unit, where an extract stream comprising
normal paraffins is generated, and a raffinate stream comprising
non-normal hydrocarbons is generated. The extract stream is passed
to an aromatics adsorption unit to selectively remove aromatic
compounds that remain in the extract stream. The aromatics
adsorption unit creates a process stream with a reduced heavy
aromatic concentration. The process stream is passed to a
separation unit to remove residual desorbent and light aromatics.
The desorbent and light aromatics are components left in the
aromatics adsorption unit during the regeneration of the aromatics
adsorbent.
[0007] Additional objects, embodiments and details of this
invention can be obtained from the following figures and detailed
description of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a process flow of the present invention showing
the improvement to achieve a high purity normal paraffin; and
[0009] FIG. 2 is the process for the regeneration of the aromatics
adsorber.
DETAILED DESCRIPTION OF THE INVENTION
[0010] A high purity heavy normal paraffin is required for some
applications. The high purity, also includes having a low aromatic
content. Conventional methods for producing a heavy normal paraffin
result in a product that contains an aromatic content greater than
0.5% by weight. The high purity heavy normal paraffins require a
purity of greater than 99.5 wt. % with an aromatic content less
than 100 ppm by weight. Conventional methods use a high pressure
hydrogenation process to saturate the aromatics, but this does not
increase the overall purity of the heavy normal paraffin.
[0011] Linear alkylbenzenes (LABs) and secondary alkane sulfonates
(SASs) are types of surfactant components used for the production
of detergents. The production of LABs requires a feedstream of
linear olefins, which in turn can be produced from linear
paraffins. The linear olefins useful for producing SASs for
detergent production have linear carbons chains in the 10 to 20
range, and preferably in the 14 to 17 range. The linear olefins for
producing LABs for detergent production have linear carbon chains
in the 10 to 20 range, and are preferably grouped to within a range
of 4 linear carbon chains, with some examples as 10 to 13, 11 to
14, and 14 toll. One source of linear paraffins in this range is
from light gas oil (LGO), which is a product stream cut from crude
oil in the 200.degree. C. to 320.degree. C. range. This also can
include hydrocarbons in the kerosene range. The present invention
takes a portion of the feedstream, either LGO or other hydrocarbon
stream, and further separates the material to provide a purified
normal paraffin stream.
[0012] The present invention, as shown in FIG. 1, is a process for
the purification of a heavy normal paraffin. The process includes
passing a hydrocarbon feedstream 8 to a prefractionation unit 10.
The prefractionation unit 10 separates the feedstream into three
streams. The unit 10 generates a first stream 12 of the heavy
hydrocarbons, a second stream 14 of light hydrocarbons, and a third
stream 16 of intermediate hydrocarbons. The intermediate
hydrocarbons are a desired selected group of hydrocarbons in the
range of C14 to C17 hydrocarbons. The third stream 16 includes
normal paraffins, aromatics, branched paraffins and other
hydrocarbons. The heavy stream 12 comprises hydrocarbons having 18
or more carbon atoms, and the light stream 14 comprises
hydrocarbons having 13 or fewer carbon atoms.
[0013] The third stream 16 is passed to a hydroprocessing unit 20,
where contaminants, such as sulfur and nitrogen are reacted over a
hydroprocessing catalyst under a hydrogen atmosphere 26 and
removed. This is done to extend the life of the adsorbent in the
adsorption separation unit 30. In addition, the hydroprocessing
unit 20 partially hydrogenates some of the unsaturated
hydrocarbons, such as olefins and aromatics. Hydrogenating a
portion of the olefins increases the paraffin content and can
increase the yields of normal paraffins. The hydroprocessing unit
20 generates an effluent stream 22 having a reduced contaminant
content. The effluent stream 22 is passed to an adsorption
separation unit 30, where normal paraffins are separated from the
non-normal paraffins and remaining types of hydrocarbons. The
adsorption separation unit 30 generates an extract stream 32 that
includes normal paraffins and desorbent, but also includes a small
amount of aromatic compounds that the process does not remove to a
sufficiently low concentration. The extract stream 32 is passed to
a paraffin extract purification adsorbent system 40 to remove a
significant portion of the residual aromatics in the adsorbent
stream 32, and to generate a purified extract stream 42 containing
normal paraffins and desorbent. The extract stream 32 is not
processed through an expensive fractionation column, but is passed
directly to the adsorbent system 40.
[0014] The purified extract stream 42 is passed to an extract
fractionation column 50 to separate the stream into a desorbent
stream 52 and a normal paraffin product stream 54. The desorbent
stream 52 is re-used in both the adsorption separation unit 30 and
the adsorbent system 40. The normal paraffin product stream 54 has
a heavy aromatic content of less than 0.5 wt %. Preferably, the
process will be operated to reduce the heavy aromatic content to
less than 100 ppm by weight. The heavy aromatics include aromatic
hydrocarbons having between 14 and 17 carbon atoms. The adsorption
units 40 eliminate the need for an extract fractionation column to
separate the extract from the desorbent. In an alternate
embodiment, the extract stream 32 can be passed to a fractionation
column before passing the extract stream to the adsorbent unit 40.
In this embodiment, the desorbent is substantially removed from the
extract stream 32, creating an extract stream with reduced
desorbent content. The extract stream with reduced desorbent
content is passed to the adsorbent unit 40 and residual aromatics
are removed.
[0015] The adsorption separation unit 30 also generates a raffinate
stream 34 that includes the desorbent, non-normal paraffins and
other hydrocarbons. The raffinate stream 34 is passed to a
raffinate fractionation column 60 to separate the raffinate stream
34 into a desorbent stream 62 and a bottoms stream 64 comprising
non-normal paraffins, and other hydrocarbons. The bottoms stream 64
can be passed to other processing units. The desorbent stream 62 is
re-used in the adsorption separation unit 30.
[0016] The adsorption separation system used for the continuous
processing of hydrocarbons uses a simulated moving bed system,
wherein the adsorption separation simulates the counter-current
contact of a feedstream with an adsorbent. In a simulated context,
the fluid flows down a column of beds, and the solid adsorbent
moves up the column of beds.
[0017] The process has four zones: an adsorption zone where the
feedstream contacts the adsorbent and selectively adsorbs the
desired components thereby creating a raffinate stream; a
purification zone where undesired components are flushed from the
system to prevent contamination of the desorption zone; a
desorption zone, where a liquid desorbent is added to displace the
adsorbed component in the adsorbent beds thereby creating an
extract stream; a buffer to prevent the contamination of liquid
from desorption zone with the liquid in the adsorption zone. More
information on the process is available in numerous patents and
references, including U.S. Pat. No. 5,912,395, which is
incorporated by reference in its entirety.
[0018] The adsorption process in the present invention uses
molecular sieving where the pores in the adsorbent are sized to
allow for normal paraffins, but non-linear molecules are prevented
from entering the pores.
[0019] The process of adsorbing heavy aromatics in the adsorbent
unit 40 generates some light aromatics in the purified extract
stream 42. The light aromatics include aromatics in the C6 to C8
range, and are light components that are used in the regeneration
of the adsorbent in the adsorbent unit 40. The purified extract
stream 42 when passed to the separation unit 50, includes in the
overhead stream 52 light aromatics which can be re-used in the
adsorbent unit 40.
[0020] The process is a continuous process, and can include two or
more adsorbers in the heavy aromatic adsorbent units 40, where at
least one adsorber is on-line and processing the extract stream 32,
and one adsorber is off-line. When an adsorber is taken off-line,
it is regenerated and later returned to on-line status as an
on-line unit is taken off-line. The regeneration process, as shown
in FIG. 2, includes a first step of passing a stream 44 of purge
material through the adsorbent unit 40. The purge stream 46 is then
passed to a fractionation unit 70. After purging the adsorbent unit
40, a desorbent stream 48 is introduced to the adsorption unit 40.
A desorption stream which is separate from the purge stream 46 is
generated carrying the heavy aromatic components to the
fractionation unit 70. In a preferred embodiment, the invention
comprises six adsorbers in the adsorbent unit 40, with four of the
adsorbers on-line, while a fifth adsorber is being purged and a
sixth adsorber is being regenerated. The process can include more
or less adsorbers in the adsorption unit 40, depending on the size
of the process streams.
[0021] The purge material can comprise a hydrocarbon stream having
a different boiling point than the material in the C14 to C17
range. A light material such as hydrocarbons in the C5 to C10 range
is appropriate for displacing larger hydrocarbons left behind in
the adsorbent unit 40. In one embodiment, a selection for the purge
stream is a mixture of n-pentane and isooctane. The adsorbent is
selected to preferentially adsorb aromatic compounds. The desorbent
needs to be selected to displace the adsorbed aromatic compound,
and to have a different boiling point from the adsorbed material. A
light aromatic compound in the C6 to C8 range is an appropriate
choice. In one embodiment, para-xylene is selected for desorbing
the heavy aromatics from the aromatics adsorption unit 40.
[0022] The choice of para-xylene is beneficial to the process, as
para-xylene is also used in the adsorption separation unit 30, to
purge material in the zone flush of the adsorption separation unit
30. The choice of purge material for the aromatics adsorption unit
40 is the same as the desorbent mixture for use in the adsorption
separation unit 30. The process benefits by having the desorbent
and purge materials do double duty in that the desorbent and purge
materials are used in both adsorption units.
[0023] The fractionation unit 70 receives the purge stream 46 and
the desorption stream which is separate from the purge stream 46 to
separate the material recovered from the adsorption unit 40 during
regeneration. The separated streams include a first stream 72
comprising the purge material, a second stream 74 comprising the
desorbent and a residual amount of the treated feedstream, and a
third stream 76 comprising the heavy aromatics in the C14 to C17
range. The heavy aromatics can be returned to the LGO process
stream, or other process units. The fractionation unit 70 can
comprise a divided wall column or can comprise two separate
columns.
[0024] While the invention has been described with what are
presently considered the preferred embodiments, it is to be
understood that the invention is not limited to the disclosed
embodiments, but it is intended to cover various modifications and
equivalent arrangements included within the scope of the appended
claims.
* * * * *