U.S. patent application number 10/328809 was filed with the patent office on 2004-06-24 for multicomponent sorption bed for the desulfurization of hydrocarbons.
Invention is credited to Osborne, R. Scott, Spivey, R. Steve, Wagner, Jon P., Weston, Eric J..
Application Number | 20040118751 10/328809 |
Document ID | / |
Family ID | 32594588 |
Filed Date | 2004-06-24 |
United States Patent
Application |
20040118751 |
Kind Code |
A1 |
Wagner, Jon P. ; et
al. |
June 24, 2004 |
Multicomponent sorption bed for the desulfurization of
hydrocarbons
Abstract
A novel hydrocarbon feedstream catalyst bed for the
desulfurization of a gas or a liquid hydrocarbon feedstream and a
process comprising passing a hydrocarbon feedstream over the
catalyst bed is described. The bed comprises at least two catalysts
having different sulfur compound affinities and/or specificities
thereby improving the overall amount of sulfur compound removal.
The process reduces the sulfur content in a gas hydrocarbon
feedstream from up to about 300 ppm to less than about 500 ppb, and
in a liquid hydrocarbon feedstream from up to about 3% to less than
about 500 ppb.
Inventors: |
Wagner, Jon P.; (Louisville,
KY) ; Weston, Eric J.; (Shepherdsville, KY) ;
Spivey, R. Steve; (Memphis, IN) ; Osborne, R.
Scott; (Louisville, KY) |
Correspondence
Address: |
Joan L. Simunic
Sud - Chemic Inc
1600 West Hill Street
Louisville
KY
40210
US
|
Family ID: |
32594588 |
Appl. No.: |
10/328809 |
Filed: |
December 24, 2002 |
Current U.S.
Class: |
208/306 ;
208/244; 208/246; 208/247; 208/299; 502/343 |
Current CPC
Class: |
C07C 7/12 20130101; C07C
7/13 20130101; C10G 25/003 20130101 |
Class at
Publication: |
208/306 ;
208/244; 208/246; 208/247; 208/299; 502/343 |
International
Class: |
C10G 025/00; C10G
029/00 |
Claims
What is claimed is:
1. A catalyst bed for the removal of contaminants from a
hydrocarbon feedstream, said catalyst bed comprising: (a) a
selective adsorbent catalyst having an affinity for a predetermined
class of chemical compounds; and (b) a general adsorbent catalyst
capable of adsorbing hydrocarbon feedstream contaminants without a
high degree of specificity, said selective adsorbent catalyst and
said general adsorbent catalyst being in tandem to form said
catalyst bed.
2. The catalyst bed of claim 1 wherein said selective adsorbent
material is selected from the group consisting of copper/zinc
catalysts, zinc oxide catalysts, copper/zinc/molybdenum oxide
catalysts, nickel aluminas, nickel silicas and combinations
thereof.
3. The catalyst bed of claim 1 wherein said general adsorbent
material is selected from the group consisting of activated carbon,
magnesium oxide, copper/manganese, silver on alumina, nickel
silicates, nickel silica/magnesia/alumina, zeolites, molecular
sieves, faujasites and combinations thereof.
4. The catalyst bed of claim 1 wherein said general adsorbent
catalyst is positioned near an inlet port of said catalyst bed.
5. The catalyst bed of claim 1 wherein said selective adsorbent
catalyst is positioned near an inlet port of said catalyst bed.
6. A catalyst bed for the removal of contaminants from a
hydrocarbon feedstream, said catalyst bed comprising a mixture of a
selective adsorbent catalyst having an affinity for a predetermined
class of chemical compounds; and a general adsorbent catalyst
capable of adsorbing hydrocarbon feedstream contaminants without a
high degree of specificity.
7. The catalyst bed of claim 6 wherein said selective adsorbent
material is selected from the group consisting of copper/zinc
catalysts, zinc oxide catalysts, copper/zinc/molybdenum oxide
catalsyts, nickel aluminas, nickel silicas and combinations
thereof.
8. The catalyst bed of claim 6 wherein said general adsorbent
material is selected from the group consisting of activated carbon,
magnesium oxide, copper/manganese, silver on alumina, nickel
silicates, nickel silica/magnesia/alumina, zeolites, molecular
sieves, faujasites and combinations thereof.
9. A process for removing contaminants from a hydrocarbon
feedstream, said process comprising the steps of: (a) providing a
catalyst bed, having an inlet port and an exit port, said catalyst
bed comprising a selective adsorption catalyst and a general
adsorption catalyst, and (b) allowing said hydrocarbon feedstream
to enter said catalyst bed through said inlet port and to exit said
catalyst bed through said exit port, said feedstream residing in
said catalyst bed for a predetermined period of time at a
predetermined temperature and pressure.
10. The process of claim 9 wherein said selective adsorbent
material is selected from the group consisting of copper/zinc
catalysts, zinc oxide catalysts, copper/zinc/molybdenum oxide
catalsyts, nickel aluminas, nickel silicas and combinations
thereof.
11. The process of claim 9 wherein said general adsorbent material
is selected from the group consisting of activated carbon,
magnesium oxide, copper/manganese, silver on alumina, nickel
silicates, nickel silica/magnesia/alumina, zeolites, molecular
sieves, faujasites and combinations thereof.
12. A catalyst bed for the removal of sulfur-containing components
from a hydrocarbon feedstream, said catalyst bed comprising: (a) a
selective adsorbent catalyst having an affinity for at least one
sulfur-containing compounds; and (b) a general adsorbent catalyst
capable of adsorbing sulfur-containing compounds in said
hydrocarbon feedstream without a high degree of specificity, said
selective adsorbent catalyst and said general adsorbent catalyst
being in tandem to form said catalyst bed.
13. The catalyst bed of claim 12 wherein said selective adsorbent
material is selected from the group consisting of copper/zinc
catalysts, zinc oxide catalysts, copper/zinc/molybdenum oxide
catalysts, nickel aluminas, nickel silicas and combinations
thereof.
14. The catalyst bed of claim 12 wherein said general adsorbent
material is selected from the group consisting of activated carbon,
magnesium oxide, copper/manganese, silver on alumina, nickel
silicates, nickel silica/magnesia/alumina, zeolites, molecular
sieves, faujasites and combinations thereof.
15. The catalyst bed of claim 12 wherein said general adsorbent
catalyst is positioned near an inlet port of said catalyst bed.
16. The catalyst bed of claim 12 wherein said selective adsorbent
catalyst is positioned near an inlet port of said catalyst bed.
17. A catalyst bed for the removal of sulfur-containing components
from a hydrocarbon feedstream, said catalyst bed comprising a
mixture of a selective adsorbent catalyst having an affinity for at
least one sulfur-containing compound; and a general adsorbent
catalyst capable of adsorbing sulfur-containing compounds in said
hydrocarbon feedstream without a high degree of specificity.
18. The catalyst bed of claim 17 wherein said selective adsorbent
material is selected from the group consisting of copper/zinc
catalysts, zinc oxide catalysts, copper/zinc/molybdenum oxide
catalsyts, nickel aluminas, nickel silicas and combinations
thereof.
19. The catalyst bed of claim 17 wherein said general adsorbent
material is selected from the group consisting of activated carbon,
magnesium oxide, copper/manganese, silver on alumina, nickel
silicates, nickel silica/magnesia/alumina, zeolites, molecular
sieves, faujasites and combinations thereof.
Description
BACKGROUND
[0001] The present invention relates to a catalyst bed for the
desulfurization of a hydrocarbon feedstream. The catalyst bed
comprises at least two catalysts, each having an affinity for
sulfur-containing compounds. When used in combination, the catalyst
bed demonstrates significant reductions in the sulfur concentration
in the feedstream. A process for reducing the concentration of
sulfur compounds in a hydrocarbon feedstream to a level of less
than about 500 ppb is also disclosed.
[0002] Hydrocarbon feed streams, such as natural gas (NG),
liquified petroleum gas (LPG) and gasoline, are used as the
starting materials for several chemical processes, many of which
utilize catalysts in one or more reaction steps. However, problems
frequently arise during the chemical processing if the hydrocarbon
feed stream also contains sulfur compounds. These sulfur compounds
can poison the reaction catalysts rendering the catalyst bed
ineffective. Nickel catalysts, which are generally useful for in
hydrogenation reactions, are especially sensitive to sulfur
poisoning on their active surfaces. Similarly, many precious metals
which are used in a variety of catalysts, are sensitive to sulfur
and can be easily poisoned by the presence of sulfur or
sulfur-containing compounds. Poisoning of the catalysts results in
longer then desired reaction times, formation of undesired side
reaction products, reduction in the life expectancy of the nickel
catalyst, and, in some instances, poor quality of the finished
product. Thus, it is beneficial to reduce the sulfur content in the
hydrocarbon feed stream before it reaches the chemical processing
catalyst bed.
[0003] However, hydrocarbon feed streams have different sources of
origin. This means that each feed stream has unique sulfur compound
contaminants and contaminants present at different concentrations.
For example, Table I shows some sulfur species commonly found in
natural gas, LPG and gasoline streams. Moreover, the sulfur species
vary not only by type of feed stream but also by source of origin.
In other words, the natural gas feed stream composition originating
in Alaska can vary significantly from the natural gas feed stream
composition originating in northern Russia.
1TABLE 1 Some sulfur species commonly found in hydrocarbon
feedstocks Species Natural Gas LPG Gasoline H.sub.2S X X --
Carbonyl Sulfide (COS) X -- -- t-Butyl Mercaptan X X -- Di-sulfides
X X X Dimethyl Sulfide (DMS) X -- -- Tetrahydrothiophene (THT) X --
X C2-C3 mercaptans X X X thiophene -- -- X C4+ mercaptans -- -- X
benzothiophenes -- -- X subs. - benzothiophenes -- -- X sulfides --
-- X X indicates present in the feedstream; -- indicates absent in
the feedstream
[0004] A number of different catalysts that are effective for
removing sulfur compounds are known in the art. For example,
activated carbon has a high capacity for ethyl mercaptans,
manganese oxide is effective for dimethyl sulfoxide removal, and
zinc oxide can be used to remove hydrogen sulfide. Other catalysts
known to be effective in desulfurization processes include carbon,
copper/zinc oxides, nickel-based sorbents, nickel oxides, zeolites,
molecular sieves and faujasites, among others. In addition,
different methods have been used to reduce the sulfur level in
feedstreams. The most commonly used procedure involves the
application of a hydrogen recycle stage to convert the
sulfur-containing compounds to H.sub.2S, and then the removal of
the sulfur compounds in a separate step. This can be an arduous and
time-consuming procedure. Thus, a better method for removal of
sulfur-containing compounds is needed. However, because of the
variations in the specific sulfur compound species and the
concentration of the sulfur compounds in the feed streams, it can
be difficult to find a single catalyst composition that is
universally effective for the removal of essentially all sulfur
compounds from gas and liquid hydrocarbon streams.
SUMMARY
[0005] The present invention is for a novel hydrocarbon feedstream
catalyst bed for the desulfurization of a gas or a liquid
hydrocarbon feedstream. The bed comprises at least two catalysts
having different sulfur compound affinities and/or specificities
thereby improving the overall amount of sulfur compound removal. In
one embodiment, the catalyst bed is configured such that the feed
stream has initial contact with a first catalyst that is more
selective or that has the greater affinity for the sulfur compound
that is present in relatively high concentration within the
feedstream. As the feedstream passes over the first catalyst, the
targeted sulfur compounds are removed generating a cleaner stream
for reaction with a second catalyst. Because the stream is cleaner
when it reaches the second catalyst, the efficiency of the second
catalyst is enhanced. In an alternative embodiment, the catalysts
are mixed within the catalyst bed. As the feedstream passes over
the catalyst bed, the sulfur compounds are adsorbed by the catalyst
having the highest affinity for the particular sulfur compound.
[0006] The present development further describes a process
comprising passing a hydrocarbon feedstream over a catalyst bed
comprising at least two catalysts having different sulfur compound
affinities and/or specificities thereby improving the overall
amount of sulfur compound removal. The process reduces the sulfur
content in a gas hydrocarbon feedstream from up to about 300 ppm to
less than about 500 ppb, and in a liquid hydrocarbon feedstream
from up to about 3% to less than about 500 ppb.
SUMMARY OF THE FIGURES
[0007] FIG. 1 is a perspective view of a catalyst bed of a
hydrocarbon feedstream desulfurization system wherein the catalyst
bed is made in accordance with the present invention and the
selective adsorbent section is positioned near the inlet port and
the general adsorbent section is positioned near the exit port;
[0008] FIG. 2 is a perspective view of a catalyst bed of a
hydrocarbon feedstream desulfurization system wherein the catalyst
bed is made in accordance with the present invention and the
general adsorbent section is positioned near the inlet port and the
selective adsorbent section is positioned near the exit port;
and
[0009] FIG. 3 is a perspective view of a catalyst bed of a
hydrocarbon feedstream desulfurization system wherein the catalyst
bed is made in accordance with the present invention and the
general adsorbent is intermixed with the selective adsorbent to
form the filter bed.
DETAILED DESCRIPTION
[0010] The present invention is for a catalyst bed that is intended
to be used to remove contaminants from a gas or liquid hydrocarbon
feedstream. As is known in the art, some of the most pervasive
contaminants in these feedstreams are sulfur-containing compounds,
such as, but not limited to, hydrogen sulfide, carbonyl sulfide,
sulfides, mercaptans, thiophenes, tert-butyl mercaptan,
di-sulfides, dimethyl sulfide, tetrahydrothiophene, ethyl
mercaptan, and benzothiophene. Many of these sulfur contaminants
not only have strong odors, making it unpleasant to work around
processes utilizing the feedstreams, but the sulfur is also
poisonous for many catalysts that use hydrocarbon starting
materials.
[0011] As shown in FIG. 1, a hydrocarbon feedstream desulfurization
system 10 includes a catalyst bed reactor 12 having an inlet port
14 and an exit port 16. The catalyst bed reactor 12 houses a
catalyst bed 20. A hydrocarbon feedstream, F, enters the reactor 12
at the inlet port 14. The hydrocarbon feedstream is in contact with
the catalyst bed 20 for a predetermined residence time, determined
by the dimensions of the bed 20 and the rate of flow of the
feedstream. As is known in the art, the catalyst bed 20 can have a
controlled temperature and pressure. The feedstream F then exits
the catalyst bed 20 through the exit port 16. As the feedstream F
passes over the bed 20, contaminants are removed from the feed
stream.
[0012] The hydrocarbon feedstream may be supplied as a gas or as a
liquid. The typical sulfur concentration of the raw gas-phase
hydrocarbon feedstream can have a sulfur concentration of up to
about 300 ppm and the liquid-phase feedstream can have a sulfur
concentration of up to about 3%. The process of the present
invention reduces the sulfur concentration to less than about 500
ppb.
[0013] Referring again to FIG. 1, in the present invention, the
catalyst bed 20 comprises a first catalyst or a general adsorbent
catalyst 22, and a second catalyst or a selective adsorbent
catalyst 24, each having an affinity for sulfur-containing
compounds. The first catalyst 24 is positioned near the inlet port
14 of the bed 20. The second catalyst 22 is positioned near the
exit port 16 of the bed 20.
[0014] The first or selective adsorbent catalyst 24 is preferably
selected based on the material's 24 specificity for a predetermined
class of chemical compounds. For example, a non-limiting list of
some selective catalyst materials 24 would include copper/zinc
catalysts, zinc oxide catalysts, copper/zinc/molybdenum oxide
catalsyts, nickel aluminas, nickel silicas or combinations thereof
As used herein, a "selective adsorbent catalyst" is a material that
fails to adsorb at least one of the sulfur compounds--ethyl
mercaptan, tert-butyl mercaptan, tetrahydrothiophene and dimethyl
sulfide--at a temperature of about 38.degree. C., a pressure of
about 15 psig, and a feedstream space velocity of not less than
about 3000 hr.sup.-1. If desired, the relative degrees of
specificity for a series of adsorbents can be graded by increasing
the reaction temperature and/or decreasing the space velocity. The
greater the temperature gradient between the adsorption of a first
sulfur-containing compound and a second sulfur-containing compound,
the greater the specificity of the selective adsorbent for the
first sulfur-containing compound. Similarly, the greater the space
velocity gradient between the adsorption of a first
sulfur-containing compound and a second sulfur-containing compound,
the greater the specificity of the selective adsorbent for the
first sulfur-containing compound.
[0015] The second or general adsorbent catalyst 22 is preferably
selected from a group of relatively materials which are capable of
adsorbing sulfur constituents without a high degree of specificity.
For example, a non-limiting list of some general adsorbent
catalysts would include activated carbon, magnesium oxide,
copper/manganese, silver on alumina, nickel silicates, nickel
silica/magnesia/alumina, zeolites, molecular sieves, faujasites and
combinations thereof, have been shown to be. As used herein, a
"general adsorbent catalyst" is a material that adsorbs ethyl
mercaptan, tert-butyl mercaptan, tetrahydrothiophene and dimethyl
sulfide at a temperature of about 38.degree. C., a pressure of
about 15 psig, and a feedstream space velocity of not less than
about 3000 hr.sup.-1.
[0016] In the embodiment of FIG. 1, when the hydrocarbon feedstream
passes over the catalyst bed 20, the hydrocarbons initially passes
over the selective adsorbent 24 where the targeted
sulfur-containing components are adsorbed by selective adsorbent
material 24. The remaining hydrocarbons then pass over the general
adsorbent 22 where other sulfur-containing components may be
retained by the adsorbent material 22. The remaining hydrocarbons
then exit the catalyst bed 20.
[0017] As shown in the embodiment of FIG. 2, a catalyst bed 120
comprises a general adsorbent catalyst 122 positioned near an inlet
port 114 and a selective adsorbent catalyst 124 positioned near an
exit port 116. With the alternative relative positioning of the
general catalyst 122 and the selective catalyst 124, the
hydrocarbon feedstream first passes over the general catalyst 122,
and then over the selective catalyst 124. If the selective
adsorbent catalyst 124 is highly selective, it will be relatively
unaffected by the presence of other sulfur-containing compounds.
However, if the selective adsorbent catalyst 124 has an affinity
for sulfur-containing compounds other than its 124 target compound,
this configuration risks allowing the selective catalyst 124 to
function in some respects as a general adsorbent, thereby
decreasing the overall efficacy of the catalyst bed 120.
[0018] FIG. 3 shows a second alternative embodiment for a catalyst
bed 220. In the bed 220, a general adsorbent catalyst 222 is
intermixed with a selective adsorbent catalyst 224 throughout the
length of the catalyst bed 220. As the hydrocarbon feedstream
passes over the catalyst bed 220, selected sulfur-containing
compounds are adsorbed preferentially onto the selective catalyst
224 leaving the general catalyst 222 available to adsorb other
sulfur-containing compounds. The bed 220 with the catalysts
intermixed is most effective when each catalyst 222, 224 has an
affinity for a particular class of sulfur-containing compounds. For
example, if the "general" catalyst preferentially adsorbs
thiophenes and the "selective" catalyst preferentially adsorbs
mercaptans, both classes of sulfur compounds can be removed as the
feedstream passes over the mixed bed.
[0019] The embodiments of FIGS. 1-3 have been presented and
described in terms of only two catalysts or adsorbents. However,
more than one catalyst can be combined to form the "general
adsorbent catalyst" and/or more than one catalyst can be combined
to form the "selective adsorbent catalyst".
[0020] Further, the embodiments of FIGS. 1-3 have been presented
and described in terms of removal of sulfur-containing compounds
from a hydrocarbon feedstream. However, the selection of the
catalyst materials can vary and the selection will be dependent on
the particular contaminants that are to be removed from the
feedstream.
[0021] From a reading of the above, one with ordinary skill in the
art should be able to devise variations to the inventive features.
For example, the catalyst bed may vary in design and equipment from
what is illustrated herein. Further, the general adsorbent catalyst
and the selective adsorbent catalyst may be optimized to a
particular hydrocarbon feedstream or contamination mixture. These
and other variations are believed to fall within the spirit and
scope of the attached claims.
* * * * *