U.S. patent application number 12/685892 was filed with the patent office on 2013-06-27 for vaporization and transportation of alkali metal salts.
This patent application is currently assigned to Fina Technology, Inc.. The applicant listed for this patent is James R. Butler, Hollie Craig, Joseph E. Pelati. Invention is credited to James R. Butler, Hollie Craig, Joseph E. Pelati.
Application Number | 20130165722 12/685892 |
Document ID | / |
Family ID | 44259026 |
Filed Date | 2013-06-27 |
United States Patent
Application |
20130165722 |
Kind Code |
A9 |
Pelati; Joseph E. ; et
al. |
June 27, 2013 |
Vaporization and Transportation of Alkali Metal Salts
Abstract
An apparatus and method for vaporizing and transporting an
alkali metal salt is shown. The apparatus has a first conduit
capable of transporting an alkali metal salt solution and a second
conduit in fluid communication with the first conduit, the second
conduit capable of transporting steam so that the alkali metal salt
is dissipated into the steam forming a solution that can be
transported, such as to a remote reaction zone. The solution can be
transported via a third conduit that is capable of being heated by
a heat source. The method can be used to add a promoter to a
dehydrogenation catalyst during a dehydrogenation reaction.
Inventors: |
Pelati; Joseph E.; (Houston,
TX) ; Butler; James R.; (League City, TX) ;
Craig; Hollie; (Seabrook, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Pelati; Joseph E.
Butler; James R.
Craig; Hollie |
Houston
League City
Seabrook |
TX
TX
TX |
US
US
US |
|
|
Assignee: |
Fina Technology, Inc.
Houston
TX
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20110172480 A1 |
July 14, 2011 |
|
|
Family ID: |
44259026 |
Appl. No.: |
12/685892 |
Filed: |
January 12, 2010 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12107748 |
Apr 22, 2008 |
|
|
|
12685892 |
|
|
|
|
Current U.S.
Class: |
585/444 ;
261/128; 261/152; 585/440 |
Current CPC
Class: |
B01J 8/02 20130101; C07C
5/32 20130101; B01F 5/0403 20130101; B01B 1/005 20130101; B01J
38/06 20130101; B01J 4/001 20130101; B01F 5/045 20130101; B01J
38/64 20130101; B01D 7/00 20130101 |
Class at
Publication: |
585/444 ;
261/152; 261/128; 585/440 |
International
Class: |
C07C 5/367 20060101
C07C005/367; B01F 3/02 20060101 B01F003/02; B01F 5/00 20060101
B01F005/00; B01D 1/14 20060101 B01D001/14; B01F 3/04 20060101
B01F003/04 |
Claims
1. An apparatus for vaporizing an alkali metal salt into steam,
comprising: a first conduit capable of transporting a first stream
of an alkali metal salt solution, the first conduit having at least
one opening through which the first stream can exit the first
conduit; a second conduit in fluid communication with the first
conduit, wherein the second conduit is capable of transporting a
second stream comprising steam; wherein as the first stream exits
the first conduit it is dissipated into the second stream forming a
third stream comprising the alkali metal salt of the first stream
in solution with the steam of the second stream; a third conduit in
fluid communication with the second conduit, wherein the third
conduit is capable of being heated by a heat source; and wherein
the third conduit is capable of transporting the third stream.
2. The apparatus of claim 1, further comprising at least one
diffuser located adjacent to the at least one opening of the first
conduit to dissipate the first stream into the second stream.
3. The apparatus of claim 1, wherein the third conduit is connected
to a fourth conduit for transporting the third stream into a fourth
stream within the fourth conduit.
4. The apparatus of claim 3 further comprising: a weir located
adjacent to the connection of the third conduit to the fourth
conduit to restrict the flow of any of the alkali metal that is not
dissipated into the second stream from entering the fourth
conduit.
5. The apparatus of claim 1, wherein the portion of the first
conduit containing the at least one opening is disposed within the
second conduit and forms a mixing chamber wherein the first stream
is dissipated into the second stream to form the third stream prior
to the third stream entering the third conduit.
6. The apparatus of claim 5, wherein the mixing chamber is capable
of being heated by a heat source.
7. The apparatus of claim 6, wherein the heat source is a steam
jacket.
8. The apparatus of claim 1, wherein the portion of the first
conduit containing the at least one opening is disposed within the
second conduit in a substantially concentric arrangement.
9. The apparatus of claim 1, wherein the heat source is a steam
jacket.
10. A method of enhancing the activity of a dehydrogenation
catalyst promoted with an alkali metal during a catalytic
dehydrogenation reaction, comprising: forming a first solution by
adding an alkali metal salt to steam utilizing an apparatus; the
apparatus having a first conduit capable of transporting a first
stream of an alkali metal salt, the first conduit having at least
one opening through which the first stream can exit the first
conduit; the apparatus having a second conduit in fluid
communication with the first conduit, wherein the second conduit is
capable of transporting a second stream comprising steam, wherein
as the first stream exits the first conduit it is dissipated into
the second stream forming the first solution containing alkali
metal salt of the first stream in solution with the steam of the
second stream; the apparatus having a third conduit in fluid
communication with the second conduit, wherein the third conduit is
capable of transporting the first solution, and capable of being
heated by a heat source; and bringing the first solution into
contact with a dehydrogenation catalyst.
11. The method of claim 10, wherein the alkali metal salt is added
in amounts sufficient to maintain substantially constant levels of
catalyst activity.
12. The method of claim 10, wherein the alkali metal salt is a
potassium salt compound.
13. The method of claim 10, wherein the catalytic dehydrogenation
reaction is the dehydrogenation of an alkyl aromatic hydrocarbon
reactant stream to obtain an alkenyl aromatic hydrocarbon.
14. The method of claim 10, wherein the alkali metal salt is added
to the second stream as a solid.
15. The method of claim 10, wherein the alkali metal salt is added
to the second stream as a liquid.
16. The method of claim 10, wherein the alkali metal salt is added
to the second stream as a vapor.
17. The method of claim 10, wherein the dehydrogenation catalyst
comprises 40-80 wt % iron oxide and 5-30 wt % alkali metal
compound.
18. The method of claim 10, wherein the alkali metal salt added is
equivalent to a continuous addition of from 0.01 to 1000 parts per
million by weight of alkali metal relative to the weight of a total
reactant stream contacting the dehydrogenation catalyst.
19. The method of claim 10, wherein the alkyl aromatic hydrocarbon
is ethylbenzene and the alkenyl aromatic hydrocarbon is
styrene.
20. A method of vaporizing and transporting an alkali metal salt
comprising: providing a first stream comprising an alkali metal
salt to a first conduit; the first conduit capable of transporting
the alkali metal salt and having at least one opening through which
the alkali metal salt can exit the first conduit; providing a
second stream comprising steam to a second conduit capable of
transporting the steam and in fluid communication with the first
conduit; wherein as the alkali metal salt exits the first conduit
it is dissipated into the second stream forming a third stream
containing alkali metal salt in solution with the steam; and
providing the third stream to a third conduit in fluid
communication with the second conduit, wherein the third conduit is
capable of transporting the third stream, wherein the third conduit
is capable of being heated by a heat source.
21. The method of claim 20, wherein the portion of the first
conduit containing the at least one opening is disposed within the
second conduit in a concentric arrangement.
22. The method of claim 20, wherein at least one diffuser located
adjacent to the at least one opening of the first conduit is used
to dissipate the first stream into the second stream.
23. The method of claim 20, wherein the third conduit of the
apparatus is connected to a fourth conduit for transporting the
third stream into contact with a fourth stream within the fourth
conduit and further comprises a weir located adjacent to the
connection of the third conduit to the fourth conduit to restrict
the flow of any of the alkali metal that is not dissipated into the
second stream from entering the fourth conduit.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present invention is related to U.S. patent application
Ser. No. 12/107,748 that was filed on Apr. 22, 2008.
FIELD
[0002] The present invention generally relates to catalytic
dehydrogenation reactions. More specifically, this invention
relates to the dehydrogenation of alkyl aromatic compounds to
produce vinyl aromatic compounds.
BACKGROUND
[0003] Catalytic dehydrogenation processes are well known in the
art. Such processes include the dehydrogenation of an alkyl
aromatic compound to yield a corresponding alkenyl aromatic
compound, and the dehydrogenation of a mono-olefin to yield a
corresponding conjugated di-olefin. A specific example of catalytic
dehydrogenation is the commonly used process to produce styrene, a
vinyl aromatic compound, by the catalytic dehydrogenation of
ethylbenzene.
[0004] Many known dehydrogenation catalysts and operating
parameters each have unique advantages and disadvantages. There are
a number of factors to consider relative to a dehydrogenation
catalyst and their particular operation, such as for example
between the level of conversion and the useful catalyst life.
Catalyst life is an important consideration in dehydrogenation
reactions. There are the costs related to the catalyst itself, such
as the unit cost of the catalyst, the useful life of the catalyst,
the ability to regenerate used catalyst, and the cost of disposing
of used catalyst. There are also the costs related to shutting down
a dehydrogenation reactor to replace the catalyst and/or to
regenerate the catalyst bed, which includes labor, materials, and
loss of productivity.
[0005] Normal catalyst deactivation can tend to reduce the level of
conversion, the level of selectivity, or both, each which can
result in an undesirable loss of process efficiency. There can be
various reasons for deactivation of dehydrogenation catalysts.
These can include the plugging of catalyst surfaces, such as by
coke or tars, which can be referred to as carbonization; the
physical breakdown of the catalyst structure; and the loss of
promoters, such as the physical loss of an alkali metal compound
from the catalyst. Depending upon the catalyst and the various
operating parameters that are used, one or more of these mechanisms
may apply.
[0006] It is generally preferred to maximize the useful catalyst
life, and there are a number of techniques or methods that are
known. One technique that is sometimes employed is to raise the
reaction temperature. This can be accomplished, for example, by
increasing the temperature of the reactant stream or by adding heat
to the reactor chamber. Such a reaction temperature increase will
generally increase the rate of reaction, which can offset the
deactivation of the catalyst, but may also have undesirable results
such as harming efficiency or selectivity. There can also be narrow
limits to the utility of this temperature-raising technique. There
may also be a mechanical temperature limit of the catalyst or the
equipment, beyond which further temperature increases can degrade
the catalyst's physical structure and/or the equipment's integrity.
As this limit is approached, the catalyst would then need to be
either replaced or regenerated by conventional ways. Conventional
practice generally involves shutting down the reactor and
physically removing the catalyst for replacement.
[0007] It would be desirable to have a catalyst regeneration method
that could be used during steady-state process conditions without
process interruption, which would maintain acceptable levels of
conversion and selectivity. It is also desirable to have an
apparatus to facilitate the addition of the catalyst life extender
to the process during steady-state process conditions. It is also
desirable to have an apparatus to facilitate the addition of the
catalyst life extender to multiple processes simultaneously.
Furthermore, it is desirable to transport the catalyst life
extender from a remote location.
SUMMARY
[0008] One embodiment of the present invention is an apparatus for
vaporizing an alkali metal salt into steam having a first conduit
capable of transporting an alkali metal salt solution, the first
conduit having at least one opening through which the solution can
exit the first conduit. A second conduit is in fluid communication
with the first conduit. The second conduit is capable of
transporting a stream that includes steam. The alkali metal salt
solution is injected concurrently into the steam forming a solution
of alkali metal salt in steam. The solution of alkali metal salt in
steam is thereafter transported in a third conduit that is in fluid
communication with the second conduit, wherein the third conduit is
capable of being heated by a heat source, such as a steam
jacket.
[0009] In an embodiment, the apparatus has at least one diffuser
located adjacent to the opening of the first conduit to dissipate
the alkali metal salt solution into the steam. The third conduit
can be connected to a fourth conduit for transporting the vaporized
alkali metal salt in steam into a stream within the fourth conduit.
The stream located within the fourth conduit can also contain
reactants for a dehydrogenation reaction of an alkyl aromatic
hydrocarbon. The apparatus may further have a weir located adjacent
to the connection to the fourth conduit to restrict the flow of any
of the alkali metal that is not dissipated into the steam from
entering the third conduit. The portion of the second conduit
containing the opening of the first conduit can form a mixing
chamber wherein the alkali metal stream can be dissipated into the
steam to form a third stream prior to the third stream entering the
third conduit. The mixing chamber portion of the second conduit can
be capable of being heated by a heat source, such as a steam
jacket. A portion of the first conduit can be disposed within the
second conduit in a substantially concentric arrangement. The
alkali metal salt can be added as a solid, liquid, or a vapor, or a
combination thereof.
[0010] Another embodiment concerns a method of enhancing the
activity of a dehydrogenation catalyst promoted with an alkali
metal, during a catalytic dehydrogenation reaction. The method
includes forming a first solution by adding an alkali metal salt to
steam utilizing an apparatus for adding the alkali metal salt into
the steam. The apparatus has a first conduit capable of
transporting a first stream of the alkali metal salt, the first
conduit having at least one opening through which the first stream
can exit the first conduit. A second conduit is in fluid
communication with the first conduit; wherein the second conduit is
capable of transporting a second stream that can include steam. The
first stream exits the first conduit and, in the second conduit, is
subjected to a heat source and simultaneously dissipated into the
second stream forming the first solution containing alkali metal
salt of the first stream in solution with the steam of the second
stream. The first solution exists the second conduit and enters a
third conduit in fluid communication with the second conduit. In
the third conduit, the first solution is further heated and
transported to a fourth conduit. In the fourth conduit, the first
solution is brought into contact with the dehydrogenation
catalyst.
[0011] The third conduit is subjected to a heat source that
supplies heat to the first solution as it is transported to the
fourth conduit. The third conduit can be subject to an amount of
heat sufficient to maintain the first solution at temperatures
between 150 and 500.degree. C. In an aspect, the third conduit
serves to transport the first solution from the second conduit to
the fourth conduit, located at a remote location. The third conduit
is also subject to an amount of heat sufficient to maintain the
first solution in a pumpable state.
[0012] The alkali metal salt can be added in amounts sufficient to
maintain substantially constant levels of catalyst activity, and in
an aspect is a potassium salt compound. The catalytic
dehydrogenation reaction can be the dehydrogenation of an alkyl
aromatic hydrocarbon reactant stream to obtain an alkenyl aromatic
hydrocarbon. The alkali metal salt can be added to the steam stream
as a solid, liquid, or vapor, or a combination thereof. In an
embodiment, the catalyst contains 40-80 wt % iron oxide and 5-30 wt
% of an alkali metal compound. The alkali metal salt can be added
in amounts equivalent to a continuous addition of 0.01 to 1000
parts per million by weight of alkali metal relative to the weight
of the total reactant stream. In an embodiment, the alkyl aromatic
hydrocarbon is ethylbenzene and the alkenyl aromatic hydrocarbon is
styrene.
[0013] Yet another embodiment is a method of vaporizing and
transporting an alkali metal salt. The method involves providing a
first stream including alkali metal salt into a first conduit
capable of transporting an alkali metal salt, the first conduit
having at least one opening through which the alkali metal salt can
exit the first conduit. A second stream that includes steam is
provided to a second conduit that is in fluid communication with
the first conduit and capable of transporting a steam input stream.
As the alkali metal salt exits the first conduit it is heated and
simultaneously dissipated into the steam input stream forming a
third stream containing vaporized alkali metal salt in solution
with the steam. The portion of the first conduit containing the
opening can be disposed within the second conduit in a
substantially concentric arrangement. There can be at least one
diffuser located adjacent to the opening of the first conduit to
dissipate the first stream into the second stream. The third stream
is sent to a third conduit in fluid communication with the second
conduit. The third conduit is subject to a heat source. The third
conduit may be connected to a fourth conduit for transporting the
third stream into contact with a fourth stream within the fourth
conduit and can further include a weir located adjacent to the
connection of the third conduit to the fourth conduit to restrict
the flow of any of the alkali metal that is not dissipated into the
second stream from entering the fourth conduit.
[0014] Still another embodiment is an apparatus for supplying a
potassium carboxylate catalyst life extender to a reaction chamber
loaded with an iron oxide based, alkali metal promoted,
dehydrogenation catalyst used to prepare a vinyl aromatic
hydrocarbon from a feed stream including an alkyl aromatic
hydrocarbon. The apparatus has a first conduit capable of
transporting a first stream of a potassium carboxylate, the first
conduit having at least one opening through which the first stream
can exit the first conduit. At least a portion of the first conduit
containing the at least one opening is disposed within a second
conduit capable of transporting a second stream that can include
steam. As the first stream exits the first conduit it is heated and
simultaneously dissipated into the second stream forming a third
stream containing vaporized potassium carboxylate of the first
stream in solution with the steam of the second stream. The third
stream containing vaporized potassium carboxylate in solution with
steam is thereafter transported in a third conduit that is
connected to the second conduit, wherein the third conduit is
connected to a heat source.
BRIEF DESCRIPTION OF DRAWINGS
[0015] FIG. 1 illustrates an embodiment of the apparatus of the
present invention for vaporizing an alkali metal salt into
steam.
[0016] FIG. 2 illustrates the lab prototype potassium acetate
vaporizer.
[0017] FIG. 3 is a plot of potassium acetate recovery versus the
vaporizer temperature using 2 mL/min water for steam and 2 mL/min
of 10% potassium acetate.
[0018] FIG. 4 is a plot of potassium acetate recovery versus the
vaporizer temperature using 2 mL/min water for steam and 2 mL/min
of 25% potassium acetate compared with the 10% potassium acetate
data of FIG. 3.
[0019] FIG. 5 is a plot of an expanded lower temperature limit
using 3 mL/min water with 1 mL/min potassium acetate solutions.
DETAILED DESCRIPTION
[0020] Promoted iron oxide catalysts are especially useful in the
dehydrogenation of alkyl aromatic hydrocarbons to alkenyl aromatic
hydrocarbons. For example, production of styrene by the
dehydrogenation of ethylbenzene can be conducted by mixing
ethylbenzene with steam, and passing the mixture through a
dehydrogenation catalyst-packed bed. In many cases, compounds of an
alkali metal, such as potassium, will be present in the
dehydrogenation catalyst. The potassium can tend to diminish the
deposition of coke on the catalyst during the dehydrogenation, and
thereby increase the useful life of the catalyst. In an aspect, the
potassium may be present typically in a quantity of at least 0.01
mole per mole iron oxide up to 1 mole per mole iron oxide. One
embodiment of a dehydrogenation catalyst contains from 30 wt % to
95 wt % iron oxide and 1 wt % to 30 wt % of potassium. Another
embodiment of a dehydrogenation catalyst contains from 40 wt % to
80 wt % iron oxide and 5 wt % to 20 wt % potassium. Other
components may also be added to the dehydrogenation catalyst to
provide further promotion, activation, or stabilization
characteristics.
[0021] The dehydrogenation of ethylbenzene is usually carried out
in the presence of steam, with the weight ratio of
steam:ethylbenzene being from 0.5:1 to 4:1, or alternatively from
0.8:1 to 2:1. The steam can serve as a heat transfer medium, and
can also stabilize an intermediate oxidation stage of the catalyst
and aid in the gasification of any organic deposits on the
catalyst, thus countering carbonization of the catalyst. A portion
of the organic deposits can be oxidized into carbon monoxide and/or
carbon dioxide.
[0022] After a fresh load of catalyst or the regeneration of an
existing catalyst, there is typically an initial period of high
catalyst activity and selectivity followed by catalyst
deactivation. There are a number of possible explanations for the
gradual deterioration of catalyst activity and one or more
mechanisms may apply in a particular process. One mechanism that
may deactivate alkali metal promoted iron-based catalysts is alkali
metal loss, wherein the alkali metal is physically released from
the catalyst and becomes entrained with the reactant stream.
Another mechanism that may deactivate alkali metal promoted
iron-based catalysts is alkali metal site contamination, that is,
the physical location of the alkali metal on the catalyst is
covered or otherwise obstructed, such as by carbonization. As
catalyst deactivation progresses, eventually the level of
conversion or selectivity, or both, fall sufficiently low that the
dehydrogenation process is no longer economically viable. At this
point the process would typically have to be shut down and the
catalyst either replaced or regenerated by conventional
methods.
[0023] Embodiments of the present invention involve adding an
amount of alkali metal compound to the process sufficient to
regenerate, stabilize, or enhance the activity of the
dehydrogenation catalyst and thereby maintain economical levels of
conversion and selectivity and reduce or delay the need for
catalyst replacement. The alkali metal compound is added to a steam
input stream prior to it entering the process. The alkali metal
compound can be added in a continuous or intermittent basis as
needed and can be utilized in conjunction with other operational
techniques such as raising the reaction temperature mentioned
above. In one embodiment the alkali metal compound is a potassium
compound. In one embodiment the alkali metal compound is a
potassium salt compound that can go into solution with the steam.
In alternate embodiments the alkali metal compound is a lithium
compound, a sodium compound, a rubidium compound, a cesium
compound, a francium compound, mixtures thereof, and salts
thereof.
[0024] Various embodiments and aspects of the present invention are
given herein. The various aspects are generally not exclusive of
each other and can be used in combination with each other.
[0025] In one embodiment the alkali metal compound that is added is
an organo potassium salt. A soluble organo potassium salt is put
into solution with steam before being added to the dehydrogenation
process. A potassium salt can be sprayed or otherwise distributed
into a stream of steam, for example super heated steam, which can
dissolve and/or vaporize the salt and create a steam solution
containing the potassium that can then be added to the
dehydrogenation process. Organo potassium salts can vaporize at
lower temperatures than non-organo potassium compounds, thereby
facilitating the distribution of potassium into the flow of steam
that is added to the dehydrogenation process. Various ways of
putting a salt compound into solution with a liquid or vapor stream
are well known in the art, all of which are considered within the
scope of this invention. Non-limiting examples of suitable organo
potassium salts include potassium acetate, potassium benzoate,
potassium citrate, potassium fumarate, potassium gluconate,
potassium lactate, potassium maleate, potassium pamoate, potassium
succinate, potassium tartrate, and mixtures thereof. Potassium salt
compounds generally have excellent water solubility, due to the
high hydration energy of the K+ ion.
[0026] The amount of alkali metal compound added is dependent upon
various factors such as the amount and purity of the reactant
stream, the quantity of catalyst charge, the run length of the
catalyst load, the dehydrogenation operating conditions, and the
particular catalyst being treated. The alkali metal compound can be
added in a substantially continuous manner, such as in an amount
equivalent to a continuous addition of from 0.01 to 1000 parts per
million by weight of alkali metal relative to the weight of the
total reactant stream. In alternate embodiments the alkali metal
compound is added in an amount equivalent to a continuous addition
of 0.01 to 750; 0.10 to 500; or 0.1 to 250 parts per million by
weight of alkali metal relative to the weight of the total reactant
stream. In some embodiments the alkali metal compound is added in
an amount equivalent to a continuous addition of 0.1 to 100 parts
per million by weight of alkali metal relative to the weight of the
total reactant stream. U.S. Pat. No. 6,936,743 to Butler, which is
incorporated herein by reference, discloses the addition of a
catalyst life extender in amounts equivalent to a continuous
addition of from 0.01 to 100 parts per million by weight of the
total alkyl aromatic hydrocarbon directed into the reactor.
[0027] The alkali metal compound can also be added in an
intermittent manner, and intermittent addition may be desirable if
the amount that is added is so small as to make continuous addition
problematic. In some instances an intermittent addition of a larger
quantity of alkali metal compound may provide superior results than
a continuous addition of a smaller quantity. In alternate
embodiments the alkali metal compound is added on an intermittent
basis in an amount from 0.1 to 10,000 or more; 1.0 to 5000; or 100
to 1000 parts per million by weight of alkali metal relative to the
weight of the reactant stream. Variations of the quantity and
manner in which the alkali metal compound are added are considered
within the scope of this invention.
[0028] An aspect of the present invention involves the transporting
of an alkali metal solution to at least one process/apparatus
within a plant. The alkali metal solution is prepared in a remote
location. The first and second conduit and mixing chamber are
remote from the fourth conduit and other apparatus/processes in a
plant. The third conduit serves to transport the alkali metal
solution from the remote location to the fourth conduit and
optionally to other apparatus/processes. A fifth, and optionally
sixth, conduit can divert at least a portion of the alkali solution
to the other apparatus/processes. In an aspect, 10 to 90 percent of
the alkali solution is diverted to the other apparatus/processes.
In another aspect, 25 to 75 percent of the alkali solution is
diverted to the other apparatus/processes. In an embodiment, the
alkali solution is simultaneously delivered to the fourth conduit
and to the other apparatus/processes.
[0029] The alkali metal solution may contain from 1 wt % to 95 wt %
of an alkali metal salt. In another aspect, the alkali metal
solution may contain from 5 wt % to 80 wt %, alternately from 5 wt
% to 55 wt % or from 5 wt % to 40 wt % of an alkali metal salt, or
alternately from 10 wt % to 30 wt % of an alkali metal salt. In a
more specific aspect, the alkali metal salt includes potassium
acetate that can be in solution with water, methanol or other
material that enables the potassium acetate solution to be pumpable
without decomposition. In an embodiment, the alkali metal solution
is a potassium acetate solution having from 1 wt % to 95 wt %
potassium acetate, alternately from 5 wt % to 80 wt %, 5 wt % to 55
wt %, 5 wt % to 40 wt % potassium acetate, or alternately from 10
wt % to 25 wt % potassium acetate.
[0030] In an embodiment, the alkali metal solution is first mixed
with steam and then the mixture is fed to a vaporizer. In another
embodiment, the alkali metal solution and steam are separately and
independently fed to a vaporizer. The vaporizer may be heated by
the steam feed itself and optionally from an additional heat
source, such as a steam jacket or a heat exchanger. The vaporizer
may be operated at temperatures ranging from 150.degree. C. to
480.degree. C. In another embodiment, the vaporizer is operated at
temperatures ranging from 200.degree. C. to 400.degree. C. The
ratio of salt solution fed to the vaporizer to steam fed to the
vaporizer may be of from 1:3 salt solution to steam to 3:1 salt
solution to steam.
[0031] In an aspect, alone or in combination with other aspects, a
heat source is connected to the mixing chamber of the second
conduit and to the third conduit and the heat source is selected
from one or more of the group consisting of a steam jacket,
electric heating element, and a radiative heat source.
[0032] Yet another embodiment is a method of revamping an existing
facility used for the dehydrogenation of ethylbenzene to make
styrene utilizing a potassium promoted iron based catalyst. The
method involves adding an apparatus to a steam input stream for
vaporizing an alkali metal salt into the steam input stream. The
apparatus has a first conduit capable of transporting an alkali
metal salt, the first conduit having at least one opening through
which the alkali metal salt can exit the first conduit. A second
conduit is in fluid communication with the first conduit, wherein
the second conduit is capable of transporting a steam input stream.
As the alkali metal salt exits the first conduit it is heated and
simultaneously dissipated into the steam input stream forming a
third stream containing vaporized alkali metal salt in solution
with the steam. The portion of the first conduit containing the
opening can be disposed within the second conduit in a
substantially concentric arrangement. The apparatus may have at
least one diffuser located adjacent to the opening of the first
conduit to dissipate the first stream into the second stream. The
third stream is sent to a third conduit in fluid communication with
the second conduit. The third conduit is subject to a heat source.
The third conduit of the apparatus may be connected to a fourth
conduit for transporting the third stream into contact with a
fourth stream within the fourth conduit and can further include a
weir located adjacent to the connection of the third conduit to the
fourth conduit to restrict the flow of any of the alkali metal that
is not dissipated into the second stream from entering the fourth
conduit.
[0033] Referring now to FIG. 1, in one illustrative embodiment 100
an alkali metal salt is supplied via line 110 and is added to an
input stream of steam via line 120 where they are combined in a
mixing chamber 130 prior to the mixture being transported down line
170 and subsequently added to the dehydrogenation process/apparatus
140. The dehydrogenation process 140 shown herein can be an input
stream to a dehydrogenation process or can be a portion of the
dehydrogenation apparatus, such as a dehydrogenation reaction zone.
The alkali metal salt can be added as a liquid solution, as a
solid, or in a vapor phase, or combinations thereof. In an aspect,
the steam may be super heated. There may also be various mixing or
agitating equipment employed within the mixing chamber 130 to
facilitate the dissolution of the alkali metal salt into the steam.
In an aspect, the mixing chamber 130 has a substantially concentric
arrangement of the alkali metal salt line 110 within the steam line
120, with the streams from the salt line and the steam line
contacting in a con-current flow pattern as shown in FIG. 1. In an
alternative embodiment, the mixing chamber 130 has a concentric
arrangement of the alkali metal salt line 110 within the steam line
120 with the streams from the salt line and the steam line
contacting in a counter-current flow pattern, or with the alkali
metal salt being sprayed or otherwise distributed within the mixing
chamber 130. The alkali metal salt line 110 can alternately be
attached at an any angle relative to the mixing chamber 130, such
as from zero degrees on one embodiment having a con-current flow
arrangement to 180 degrees on one embodiment having a
counter-current arrangement, or alternatively on a 30 degree to 45
degree angle, or may be perpendicular to the mixing chamber 130
with the alkali metal salt being sprayed or otherwise distributed
through an injector head. In an aspect, mixing chamber 130 is
subjected to a heat source 180. Heat source 180 can include a steam
jacket or an electrical heating element.
[0034] In the embodiment shown in FIG. 1, there is shown an
optional diffuser 150 that can be used to dissipate the alkali
metal salt within the steam stream in the mixing chamber 130. As
used herein the term "diffuser" means any apparatus that acts to
alter the flow path of the alkali metal salt to assist in its
dissipation within the steam. The diffuser may decelerate the rate
of flow, impart turbulence within the flow and/or impart a change
in direction of the flow, or a combination thereof. The optional
diffuser 150 may be of any shape to assist in dissipating the
alkali metal salt within the steam stream. The diffuser may have an
angled or conical shape, such as shown in FIG. 1, to deflect and
distribute the alkali metal salt in a radial direction within the
steam stream.
[0035] In an aspect, line 170 is subjected to a heat source 182.
Heat source 182 can include a steam jacket or an electrical heating
element. In an embodiment, this transport line, line 170, is heated
at temperatures ranging from 200.degree. C. to 400.degree. C. In an
optional embodiment, lines 190(a,b) are used to transport at least
a portion of the mixture in line 170 to another process/apparatus
within a plant. There is also shown an optional weir 160 that can
be used to restrict the flow of any alkali metal salt that is not
in solution with the steam from entering the dehydrogenation
process/apparatus 140. As used herein the term "weir" means any
apparatus that restricts the flow of any alkali metal salt that is
not in solution with the steam from entering the dehydrogenation
process. The weir may inhibit the rate of flow of a portion of the
flow that may contain alkali metal salt that is not fully in
solution, such as in one embodiment the lower portion of the flow
stream where heavier materials, such as alkali metal salt that is
not in solution may settle. The mixture of alkali metal salt and
steam can be added directly to a dehydrogenation reactor or to an
input stream of the dehydrogenation process. Other ways of adding
the alkali metal to the steam can include the heating and
vaporizing of the alkali metal salt into the steam stream.
[0036] Dehydrogenation catalysts containing iron oxide and alkali
metal compounds are well known in the art and are available
commercially from various sources such as: BASF Corporation;
Criterion Catalyst Company, L.P.; and Sud Chemie, Inc. These and
similar catalysts are considered within the scope of this
invention.
EXAMPLES
[0037] The embodiments having been generally described, the
following examples are given as particular embodiments of the
disclosure and to demonstrate the practice and advantages thereof.
It is understood that the examples are given by way of illustration
and are not intended to limit the specification or the claims in
any manner.
[0038] A lab prototype of a potassium acetate vaporizer used for
injection of the potassium acetate into a styrene catalyst feed has
been constructed and used to evaluate process conditions. This
prototype design incorporates the injection of a liquid potassium
salt solution into a concurrent flow of steam at the inlet of a
relatively large vessel. Transport of the vaporized potassium salt
stream was simulated by attaching a length of heated tubing to the
outlet of the vaporizer. The effluent was collected and
gravimetrically evaluated for salt recovery. Suitable temperature
ranges were developed for the vaporizer and the transport tube for
both 10 and 25% potassium acetate solutions.
[0039] An embodiment of the lab prototype potassium acetate
vaporizer system 200 is shown in FIG. 2. Water 210 and potassium
acetate solution 212 were added to the system 200 using
continuous-flow dual syringe pumps. The body 216 was a 75 mL
pressure sample vessel with 1/4-inch LPT fittings on each end. The
inlet was a bored-through "T" fitting 214 with a 1/16-inch tube
inserted through to the edge of the fitting inside the body 216 for
addition of the potassium acetate solution. Water was pumped into
coiled tubing 218 that was inside the furnace to create the diluent
stream that was then introduced to the "T" fitting 214 behind the
potassium acetate introduction. The vaporizer effluent was sent
through a transport tube 220 that is of 3 feet in length of
1/4-inch tubing that has been spiral-coiled 222. The vaporizer 216
and transport tube 220, 222 were located inside a 4-zone furnace.
The first zone 1 housed the vaporizer vessel while the other three
zones 2, 3, 4 contained the transport tube 220, 222. Zone 1 was
separated from zones 2-4 by a plug of insulation. The transport
tube 224 that left the furnace was connected to a chilled water
condenser 226. A collection bottle 228 was attached to the
condenser 226 to collect the liquid product.
[0040] The vaporizer experiments began by heating the vaporizer and
transport tube to the desired temperatures and then introducing the
water for the steam. Once steady temperatures were achieved, the
potassium acetate addition started; this was the start time for the
experiment. The experiments lasted for 2-4 hours with total
collection of the liquid effluent into a tared bottle. The liquid
was sampled for chemical analysis. Then the solution was evaporated
in a drying oven to obtain the amount of potassium acetate. An
Inductively Coupled Plasma (ICP) analysis was used to confirm the
salt quantity. The experimental data are shown in Table 1
below.
TABLE-US-00001 TABLE 1 Vaporization Data using a Transfer Line and
Condenser Vaporizer Vaporizer Transtube Salt Salt Carrier Salt Salt
Temp Temp Temp Weight Solution Steam Time Collected Theoretical
Percent Data (.degree. C.) (.degree. F.) (.degree. C.) Percent
(mL/min) (mL/min) (min) (g) (g) Yield Sep. 4, 2008 400 752 200 10 2
2 240 29.82 50.11 59.51 Sep. 4, 2008 450 842 200 10 2 2 173 36.32
36.12 100.55 Sep. 5, 2008 450 842 200 10 2 2 135 28.84 28.19 102.31
Sep. 5, 2008 465 869 200 10 2 2 130 24.44 27.14 90.04 Sep. 8, 2008
475 887 200 10 2 2 146 29.68 30.48 97.36 Sep. 8, 2008 485 905 200
10 2 2 136 26.69 28.40 93.99 Sep. 9, 2008 495 923 200 10 2 2 154
28.84 32.16 89.69 Sep. 9, 2008 505 941 200 10 2 2 195 28.8 40.72
70.73 Sep. 12, 2008 515 959 200 10 2 2 131 11.06 27.35 40.43 Sep.
12, 2008 525 977 200 10 2 2 120 46.19 25.06 184.35 Sep. 23, 2008
515 959 200 10 2 2 150 11.35 31.32 36.24 Sep. 27, 2008 460 860 200
10 2 2 180 34.49 37.58 91.77 Sep. 27, 2008 470 878 200 10 2 2 138
26.49 28.81 91.93 Sep. 29, 2008 490 914 200 10 2 2 127 20.43 26.52
77.04 Sep. 29, 2008 495 923 200 10 2 2 142 18.22 29.65 61.45 Sep.
29, 2008 505 941 200 10 2 2 131 22.69 27.35 82.95 Oct. 1, 2008 455
857 200 10 2 2 136 30.57 28.40 107.65 Oct. 1, 2008 475 887 200 10 2
2 137 28.26 28.61 98.79 Oct. 3, 2008 390 734 200 10 2 2 129 29.67
26.94 110.15 Oct. 3, 2008 380 716 200 10 2 2 123 24.39 25.68 94.97
Oct. 4, 2008 370 698 200 10 2 2 120 25.41 25.06 101.41 Oct. 4, 2008
360 680 200 10 2 2 122 24.19 25.47 94.96 Oct. 4, 2008 350 662 200
10 2 2 122 24.08 25.47 94.53 Oct. 6, 2008 455 857 200 10 2 2 140
27.88 29.23 95.37 Oct. 6, 2008 490 914 200 10 2 2 129 21.16 26.94
78.56 Oct. 7, 2008 340 644 200 10 2 2 122 25.68 25.47 100.81 Oct.
8, 2008 425 797 200 10 2 2 123 24.29 25.68 94.58 Oct. 8, 2008 340
644 200 10 2 2 121 24.05 25.26 95.19 Oct. 9, 2008 330 626 200 10 2
2 125 26.06 26.10 99.85 Oct. 9, 2008 320 608 200 10 2 2 141 28.26
29.44 95.99 Oct. 11, 2008 200 392 200 10 2 2 123 24.95 25.68 97.15
Oct. 11, 2008 200 392 200 10 2 2 124 24.5 25.89 94.63 Oct. 11, 2008
200 392 200 10 2 2 120 23.77 25.06 94.87 Oct. 16, 2008 500 932 200
10 1 2 198 9.67 20.67 46.78 Oct. 20, 2008 500 932 200 10 1 3 127 0
13.26 0.00 Oct. 21, 2008 450 842 200 10 1 1 428 39.4 44.68 88.18
Oct. 28, 2008 180 356 200 10 2 2 146 3.33 30.48 10.92 Nov. 2, 2008
350 662 200 25 2 2 120 64.54 62.64 103.03 Nov. 2, 2008 400 752 200
25 2 2 124 69.33 64.73 107.11 Nov. 2, 2008 450 842 200 25 2 2 126
66.65 65.77 101.33 Nov. 11, 2008 400 752 200 10 2 2 152 39.06 31.74
112.31 Nov. 15, 2008 400 752 200 10 2 2 142 28.14 29.65 94.91 Dec.
9, 2008 200 392 200 10 1 3 141 16.73 14.72 113.65 Dec. 10, 2008 180
356 200 10 1 3 230 25.75 24.01 107.24 Dec. 10, 2008 170 338 200 10
1 3 181 19.67 18.90 104.09 Dec. 11, 2008 160 320 200 10 1 3 137
13.99 14.30 97.81 Dec. 12, 2008 150 302 200 10 1 3 135 13.73 14.09
97.42 Jan. 29, 2008 200 392 200 25 2 2 164 89.43 85.608 104.46 Jan.
29, 2008 200 392 200 25 1 3 110 29.46 28.71 102.61 Feb. 3, 2008 175
347 200 25 1 3 182 49.61 47.50 104.44 Feb. 3, 2008 150 302 200 25 1
3 123 32.29 32.10 100.58
Example 1
[0041] A variety of vaporizer temperatures were conducted to
determine an effective operating range for the vaporization of
potassium acetate. Most of the experiments were conducted with a 2
mL/min flow of water for the carrier steam and 2 mL/min of
potassium acetate solution. The potassium acetate solution was
injected into the carrier steam at the inlet of the vaporizer and
the stream is condensed and collected at the outlet. The collected
effluent solution was evaporated in a drying oven. The recovered
salt was weighed and compared with the theoretical amount
expected.
[0042] FIG. 3 shows the results for the investigation of viable
vaporizer operating temperatures for a 10% potassium acetate
solution. Potassium acetate recovery was used as the critical
measurement. A successful experiment would show 100% potassium
acetate recovery. Lower recovery numbers indicate that the
potassium acetate was deposited in the apparatus and not fully
entrained in the vapor phase. The safe operating range is from
200-480.degree. C. using 10% potassium acetate. Above 480.degree.
C., the potassium acetate is not thermally stable, thereby leading
to the formation of KOH and K.sub.2CO.sub.3 and deposition. Below
200.degree. C., the vapor pressure of potassium acetate may be too
low or there is insufficient heat for vaporization.
[0043] The transfer tube was heated by different furnace zones than
those used by the vaporizer. Testing of earlier versions of the
vaporizer system was conducted with a transfer tube temperature at
400.degree. C. initially. The lowering of the transfer tube
temperature to 200.degree. C. resulted in no changes in salt
recovery results. The 200.degree. C. transfer tube temperature was
employed for all remaining testing as shown in Table 1.
[0044] The use of high concentration potassium acetate solution may
bring benefits in capital and the operational costs of a vaporizer.
For those reasons, a 25% potassium acetate solution was used in the
vaporizer. FIG. 4 shows the results of the 25% potassium acetate
solution overlaid with those of the 10% solution. The 25% potassium
acetate can be used over this same operational range as the 10%
solution.
[0045] On a weight basis, there was only 5 wt % potassium acetate
in the effluent of the 2 mL/min water and 2 mL/min 10% potassium
acetate experiment. This amounted to only about 2% K correcting for
the acetate ion. On a molar basis, the effluent contained less than
1 mol % K due to the molecular weight differences. For the
corresponding 25% potassium acetate experiments, the corresponding
numbers were 12.5 wt % potassium acetate or 5 wt % K in the
effluent. The K molar percent was about 2.5%, also. The molar
percentages of potassium acetate in the gas phase correlates
directly with the partial pressure so the vaporizer will show a
very low partial pressure of potassium acetate, which should help
the vaporization process.
Example 2
[0046] Other experiments were conducted with higher water flows and
lower potassium acetate flows than that of Example 1. These
experiments were done for both 10% and 25% potassium acetate. The
water was increased to 3 mL/min and the potassium acetate solution
decreased to 1 mL/min. This maintained the total flow to the
vaporizer, but with different feed ratios. This data is shown in
FIG. 5. The higher ratio of steam to potassium acetate solution
allowed the successful vaporization at 150.degree. C. for both 10%
and 25% potassium acetate.
[0047] As used herein, the term "conversion" means in a
quantitative sense the fraction, in % mole, of the reactant that is
converted.
[0048] The term "selectivity" means the ability of the catalyst to
selectively produce higher levels of a desirable product and lower
levels of an undesirable product, for example to selectively
dehydrogenate ethylbenzene to produce styrene instead of toluene or
benzene.
[0049] The term "activity" means the ability of the catalyst to
convert a certain percentage of the reactants for each pass of
feedstock over the catalyst, for example to convert a certain
percentage of the ethylbenzene to aromatics for each pass of
feedstock over the catalyst.
[0050] Depending on the context, all references herein to the
"invention" may in some cases refer to certain specific embodiments
only. In other cases it may refer to subject matter recited in one
or more, but not necessarily all, of the claims. While the
foregoing is directed to embodiments, versions and examples of the
present invention, which are included to enable a person of
ordinary skill in the art to make and use the inventions when the
information in this patent is combined with available information
and technology, the inventions are not limited to only these
particular embodiments, versions and examples. Other and further
embodiments, versions and examples of the invention may be devised
without departing from the basic scope thereof and the scope
thereof is determined by the claims that follow.
* * * * *