U.S. patent application number 10/970114 was filed with the patent office on 2005-03-17 for desulfurization and novel sorbents for same.
Invention is credited to Khare, Gyanesh P..
Application Number | 20050059548 10/970114 |
Document ID | / |
Family ID | 23509239 |
Filed Date | 2005-03-17 |
United States Patent
Application |
20050059548 |
Kind Code |
A1 |
Khare, Gyanesh P. |
March 17, 2005 |
Desulfurization and novel sorbents for same
Abstract
Particulate sorbent compositions comprising a mixture of zinc
oxide, silica, alumina and a substantially reduced valence cobalt
are provided for the desulfurization of a feedstream of
cracked-gasoline or diesel fuels in a desulfurization zone by a
process which comprises the contacting of such feedstreams in a
desulfurization zone followed by separation of the resulting low
sulfur-containing stream and sulfurized-sorbent and thereafter
regenerating and activating the separated sorbent before recycle of
same to the desulfurization zone.
Inventors: |
Khare, Gyanesh P.;
(Bartlesville, OK) |
Correspondence
Address: |
ConocoPhillips Company - IP Legal
P.O. Box 2443
Bartlesville
OK
74005
US
|
Family ID: |
23509239 |
Appl. No.: |
10/970114 |
Filed: |
October 21, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10970114 |
Oct 21, 2004 |
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10255227 |
Sep 26, 2002 |
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10255227 |
Sep 26, 2002 |
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09689975 |
Oct 13, 2000 |
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6482314 |
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09689975 |
Oct 13, 2000 |
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09382502 |
Aug 25, 1999 |
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6184176 |
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Current U.S.
Class: |
502/406 |
Current CPC
Class: |
B01D 2256/24 20130101;
B01J 20/3078 20130101; B01D 2253/106 20130101; B01D 2253/104
20130101; B01J 20/3236 20130101; B01J 37/04 20130101; B01D 2253/34
20130101; B01J 37/18 20130101; B01J 38/12 20130101; C10G 25/003
20130101; B01D 2255/20746 20130101; B01D 53/02 20130101; B01J
2220/42 20130101; B01J 20/3433 20130101; B01J 20/3204 20130101;
B01J 20/06 20130101; B01J 20/28016 20130101; B01J 20/3458 20130101;
B01D 53/48 20130101; B01J 23/80 20130101; B01J 37/0072 20130101;
B01D 2257/30 20130101; B01J 20/0225 20130101; B01D 2255/20792
20130101; B01D 2253/1122 20130101; B01J 20/08 20130101; B01J 23/94
20130101; B01J 37/0201 20130101; B01D 2253/1124 20130101; B01J
20/103 20130101 |
Class at
Publication: |
502/406 |
International
Class: |
B01J 020/08 |
Claims
That which is claimed is:
1. A sorbent composition for removal of sulfur from cracked
gasolines and diesel fuels which is comprised of: (a) zinc oxide;
(b) silica; (c) alumina; and (d) cobalt wherein the valence of
essentially all of the cobalt therein is zero such that the reduced
cobalt-containing composition will affect the removal of sulfur
from a stream of cracked-gasoline or diesel fuel when said stream
is contacted with said reduced cobalt-containing composition,
wherein said zinc oxide is present in an amount in the range of
about 45 to about 60 weight percent, said silica is present in an
amount in the range of about 15 to 60 weight percent, said alumina
is present in an amount of 5.0 to about 15 weight percent and said
cobalt is present in an amount in the range of about 15 to about 40
weight percent.
2. A sorbent composition in accordance with claim 1 wherein said
zinc oxide is present in an amount of about 38 weight percent, said
silica is present in an amount in the range of about 31 weight
percent, said alumina is present in an amount of about 8 weight
percent and said cobalt is present in an amount of about 30 weight
percent.
3. A sorbent composition in accordance with claim 1 wherein said
composition is a particulate in the form of one of granule,
extrudate, tablet, sphere, pellet or microsphere.
4. A sorbent composition suitable for removal of sulfur from
cracked gasolines and diesel fuels which is comprised of: (a) zinc
oxide; (b) silica; (c) alumina; and (d) cobalt wherein the valence
of essentially all of the cobalt therein is zero such that the
reduced cobalt-containing composition will affect the removal of
sulfur from a stream of cracked-gasoline or diesel fuel when said
stream is contacted with said reduced cobalt-containing
composition; wherein said zinc oxide is present in amount in the
range of about 10 to about 90 weight percent; wherein said silica
is present in an amount in the range of about 5 to about 85 weight
percent; wherein said alumina is present in an amount in the range
from about 5.0 to about 30 weight percent; and wherein at least a
portion of the composition is calcined to convert at least a
portion of the alumina to an aluminate.
5. A sorbent composition suitable for removal of sulfur from
cracked gasolines and diesel fuels consisting essentially of: (a)
zinc oxide; (b) silica; (c) alumina; and (d) cobalt wherein the
valence of essentially all of the cobalt therein is zero such that
the reduced cobalt-containing composition will affect the removal
of sulfur from a stream of cracked-gasoline or diesel fuel when
said stream is contacted with said reduced cobalt-containing
composition; wherein said zinc oxide is present in amount in the
range of about 10 to about 90 percent; wherein said silica is
present in an amount in the range of about 5 to about 85 weight
percent; wherein said alumina is present in an amount in the range
from about 5.0 to about 30 weight percent; and wherein at least a
portion of the composition is calcined to convert at least a
portion of the alumina to an aluminate.
6. A sorbent composition comprising: (a) a support formed from a
calcined mixture of zinc oxide, silica, and alumina; and (b)
cobalt.
7. The sorbent composition of claim 6, wherein said cobalt is
present in a substantially reduced valence state and in an amount
which effects the removal of sulfur from a stream of gasoline
and/or diesel fuel when contacted with the same under
desulfurization conditions.
8. The sorbent composition of claim 6, wherein said sorbent
composition comprises substantially no cobalt oxide.
9. The sorbent composition of claim 6, wherein said cobalt is
incorporated on and/or in said support.
10. The sorbent composition of claim 6, wherein said cobalt is
impregnated on and/or in said support.
11. The sorbent composition of claim 6, wherein said silica is
selected from the group consisting of diatomite, silicalite, silica
colloid, flame-hydrolyzed silica, hydrolyzed silica, silica gel,
precipitated silica, and combinations of two or more thereof.
12. The sorbent composition of claim 11, wherein said silica
comprises diatomite.
13. The sorbent composition of claim 6, wherein said alumina is
selected from the group consisting of colloidal aluminas, aluminas
produced by the dehydration of alumina hydrates, and combinations
thereof.
14. The sorbent composition of claim 6, wherein at least a portion
of said alumina is present as an aluminate due to calcination of
said support.
15. The sorbent composition of claim 6, wherein said zinc oxide is
present in an amount in the range of about 45 to about 60 weight
percent, said silica is present in an amount in the range of about
15 to 60 weight percent, said alumina is present in an amount of
5.0 to about 15 weight percent and said cobalt is present in an
amount in the range of about 15 to about 40 weight percent.
16. A sorbent composition comprising: (a) zinc oxide; (b) silica;
(c) an aluminate; and (d) cobalt.
17. The sorbent composition of claim 16, wherein said cobalt is
present in a substantially reduced valence state and in an amount
which effects the removal of sulfur from a stream of gasoline
and/or diesel fuel when contacted with the same under
desulfurization conditions.
18. The sorbent composition of claim 16, wherein said zinc oxide,
silica, and aluminate are intimately mixed to form a support.
19. The sorbent composition of claim 18, wherein said cobalt is
present on and/or in said support.
20. The sorbent composition of claim 16, wherein said zinc oxide is
present in an amount in the range of about 45 to about 60 weight
percent, said silica is present in an amount in the range of about
15 to 60 weight percent, said aluminate is present in an amount of
5.0 to about 15 weight percent and said cobalt is present in an
amount in the range of about 15 to about 40 weight percent.
21. The sorbent composition of claim 16, wherein at least a portion
of the aluminate is formed by the calcination of alumina.
22. The sorbent composition of claim 21, wherein said alumina is
selected from the group consisting of colloidal aluminas, aluminas
produced by the dehydration of alumina hydrates, and combinations
thereof.
23. The sorbent composition of claim 16, wherein said silica is
selected from the group consisting of diatomite, silicalite, silica
colloid, flame-hydrolyzed silica, hydrolyzed silica, silica gel,
precipitated silica, and combinations of two or more thereof.
24. The sorbent composition of claim 23, wherein said silica
comprises diatomite.
25. The sorbent composition of claim 16, wherein said sorbent
composition comprises substantially no cobalt oxide.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/255,227, filed Sep. 26, 2002, which is a
divisional of U.S. patent application Ser. No. 09/689,975, filed
Oct. 13, 2000, which is a divisional of U.S. patent application
Ser. No. 09/382,502, filed Aug. 25, 1999, all incorporated by
reference herein.
FIELD OF THE INVENTION
[0002] This invention relates to the removal of sulfur from fluid
streams of cracked-gasolines and diesel fuels. In another aspect
this invention relates to sorbent compositions suitable for use in
the desulfurization of fluid streams of cracked-gasolines and
diesel fuel. A further aspect of this invention relates to a
process for the production of sulfur sorbents for use in the
removal of sulfur bodies from fluid streams of cracked gasolines
and diesel fuels.
BACKGROUND OF THE INVENTION
[0003] The need for cleaner burning fuels has resulted in a
continuing world wide effort to reduce sulfur levels in gasoline
and diesel fuels. The reducing of gasoline and diesel sulfur is
considered to be a means for improving air quality because of the
negative impact the fuel sulfur has on the performance of
automotive catalytic converters. The presence of oxides of sulfur
in automotive engine exhaust inhibits and may irreversibly poison
noble metal catalysts in the converter. Emissions from an
inefficient or poisoned converter contain levels of non-combusted,
non-methane hydrocarbon and oxides of nitrogen and carbon monoxide.
Such emissions are catalyzed by sunlight to form ground level
ozone, more commonly referred to as smog.
[0004] Most of the sulfur in gasoline comes from the thermally
processed gasolines. Thermally processed gasolines such, as for
example, thermally cracked gasoline, visbreaker gasoline, coker
gasoline and catalytically cracked gasoline (hereinafter
collectively called "cracked-gasoline") contains in part olefins,
aromatics, and sulfur-containing compounds.
[0005] Since most gasolines, such as for example automobile
gasolines, racing gasolines, aviation gasoline and boat gasolines
contain a blend of at least in part cracked-gasoline, reduction of
sulfur in cracked-gasoline will inherently serve to reduce the
sulfur levels in such gasolines.
[0006] The public discussion about gasoline sulfur has not centered
on whether or not sulfur levels should be reduced. A consensus has
emerged that lower sulfur gasoline reduces automotive emissions and
improves air quality. Thus the real debate has focused on the
required level of reduction, the geographical areas in need of
lower sulfur gasoline and the time frame for implementation.
[0007] As the concern over the impact of automotive air pollution
continues, it is clear that further efforts to reduce the sulfur
levels in automotive fuels will be required. While the current
gasoline products contain about 330 part per million with continued
efforts by the Environmental Protection Agency to secure reduced
levels, it has been estimated that gasoline will have to have less
than 50 part per million of sulfur by the year 2010. (See Rock, K.
L., Putman H. M., Improvements in FCC Gasoline Desulfurization via
Catalytic Distillation" presented at the 1998 National Petroleum
Refiners Association Annual Meeting (AM-98-37)).
[0008] In view of the ever increasing need to be able to produce a
low sulfur content automotive fuel, a variety of processes have
been proposed for achieving industry compliance with the Federal
mandates.
[0009] One such process which has been proposed for the removal of
sulfur from gasoline is called hydrodesulfurization. While
hydrodesulfurization of gasoline can remove sulfur-containing
compounds, it can result in the saturation of most, if not all, of
the olefins contained in the gasoline. This saturation of olefins
greatly affects the octane number (both the research and motor
octane number) by lowering it. These olefins are saturated due to,
in part, the hydrodesulfurization conditions required to remove
thiophenic compounds (such as, for example, thiophene,
benzothiophene, alkyl thiophenes, alkylbenzothiphenes and alkyl
dibenzothiophenes), which are some of the most difficult
sulfur-containing compounds to removed. Additionally, the
hydrodesulfurization conditions required to remove thiophenic
compounds can also saturate aromatics.
[0010] In addition to the need for removal of sulfur from
cracked-gasolines, there is also presented to the petroleum
industry a need to reduce the sulfur content of diesel fuels. In
removing sulfur from diesel by hydrodesulfurization, the cetane is
improved but there is a large cost in hydrogen consumption. This
hydrogen is consumed by both hydrodesulfurization and aromatic
hydrogenation reactions.
[0011] Thus there is a need for a process wherein desulfurization
without hydrogenation of aromatics is achieved so as to provide a
more economical process for the treatment of diesel fuels.
[0012] As a result of the lack of success in providing successful
and economically feasible process for the reduction of sulfur
levels in both cracked-gasolines and diesel fuels, it is apparent
that there is still needed a better process for the desulfurization
of both cracked-gasolines and diesel fuels which has minimal affect
of octane while achieving high levels of sulfur removal.
[0013] It is thus an object of the present invention to provide a
novel sorbent system for the removal of sulfur from fluid streams
of cracked-gasolines and diesel fuels.
[0014] Another object of this invention is to provide a process for
the production of novel sorbents which are useful in the
desulfurization of such fluid streams.
[0015] Another object of this invention is to provide a process for
the removal of sulfur-containing compounds from cracked-gasolines
and diesel fuels which minimize saturation of olefins and aromatics
therein.
[0016] A still further object of this invention is to provide a
desulfurized cracked-gasoline that contains less than about 100
parts per million of sulfur based on the weight of the desulfurized
cracked-gasoline and which contains essentially the same amount of
olefins and aromatics as were in the cracked-gasoline from which it
is made.
[0017] Other aspects, objects and the several advantages of this
invention will be apparent from the following description of the
invention and the appended claims.
SUMMARY OF THE INVENTION
[0018] The present invention is based upon our discovery that
through the utilization of cobalt in a substantially reduced
valence state, preferably zero, in a sorbent composition there is
achieved a novel sorbent composition which permits the ready
removal of sulfur from streams of cracked-gasolines or diesel fuels
with a minimal effect on the octane rating of the treated
stream.
[0019] Accordingly, in one aspect of the present invention there is
provided a novel sorbent suitable for the desulfurization of
cracked-gasolines or diesel fuels which is comprised of zinc oxide,
silica, alumina and cobalt wherein the valence of the cobalt is
substantially reduced and such reduced valence cobalt is present in
an amount to permit the removal of sulfur from cracked-gasolines or
diesel fuels.
[0020] In accordance with another aspect of the present invention,
there is provided a process for the preparation of a novel sorbent
composition which comprises admixing zinc oxide, silica and alumina
so as to form a wet mix, dough, paste or slurry thereof,
particulating the wet mix, dough, paste or slurry thereof so as to
form a particulate granule, extrudate, tablet, sphere, pellet or
microsphere thereof; drying the resulting particulate; calcining
the dried particulate; impregnating the resulting solid particulate
with a cobalt or a cobalt-containing compound; drying the resulting
impregnated solid particulate composition, calcining the dried
particulate composition and reducing the calcined product with a
suitable reducing agent, such as hydrogen, so as to produce a
sorbent composition having a substantial zero valence cobalt
content in an amount which is sufficient to permit the removal with
same of sulfur from a cracked-gasoline or diesel fuel stream.
[0021] In accordance with a further aspect of the present
invention, there is provided a process for the desulfurization of a
cracked-gasoline or diesel fuel stream which comprises
desulfurizing in a desulfurization zone a cracked-gasoline or
diesel fuel with a solid-reduced cobalt metal-containing sorbent,
separating the desulfurized cracked-gasoline or diesel fuel from
the sulfurized sorbent, regenerating at least a portion of the
sulfurized-solid-reduced cobalt metal metal-containing sorbent to
produce a regenerated desulfurized solid cobalt metal
metal-containing sorbent; activating at least a portion of the
regenerated desulfurized solid cobalt metal-containing sorbent to
produce a solid reduced cobalt metal metal-containing sorbent; and
thereafter returning at least a portion of the resulting reduced
cobalt metal-containing sorbent to the desulfurization zone.
DETAILED DESCRIPTION OF THE INVENTION
[0022] The term "gasoline" as employed herein is intended to mean a
mixture of hydrocarbons boiling from about 100.degree. F. to
approximately 400.degree. F. or any fraction thereof. Such
hydrocarbons will include, for example, hydrocarbon streams in
refineries such as naphtha, straight-run naphtha, coker naphtha,
catalytic gasoline, visbreaker naphtha, alkylate, isomerate or
reformate.
[0023] The term "cracked-gasoline" as employed herein is intended
to mean hydrocarbons boiling from about 100.degree. F. to
approximately 400.degree. F. or any fraction thereof that are
products from either thermal or catalytic processes that crack
larger hydrocarbon molecules into smaller molecules. Examples of
thermal processes include coking, thermal cracking and visbreaking.
Fluid catalytic cracking and heavy oil cracking are examples of
catalytic cracking. In some instances the cracked-gasoline may be
fractionated and/or hydrotreated prior to desulfurization when used
as a feed in the practice of this invention.
[0024] The term "diesel fuel" as employed herein is intended to
mean a fluid composed of a mixture of hydrocarbons boiling from
about 300.degree. F. to approximately 750.degree. F. or any
fraction thereof. Such hydrocarbon streams include light cycle oil,
kerosene,jet fuel, straight-run diesel and hydrotreated diesel.
[0025] The term "sulfur" as employed herein is intended to mean
those organosulfur compounds such as mercaptans or those thiophenic
compounds normally present in cracked gasolines which include among
others thiophene, benzothiophene, alkyl thiophenes, alkyl
benzothiophenes and alkyldibenzothiophenes as well as the heavier
molecular weights of same which are normally present in a diesel
fuel of the types contemplated for processing in accordance with
the present invention.
[0026] The term "gaseous" as employed herein is intended to mean
that state in which the feed cracked-gasoline or diesel fuel is
primarily in a vapor phase.
[0027] The term "substantially reduced cobalt valence" as employed
herein is intended to mean that a large portion of the valence of
the cobalt component of the composition is reduced to a value of
less than 3, preferably zero.
[0028] The present invention is based upon the discovery of
applicants that a substantially reduced valence cobalt component in
a particulate composition comprising zinc oxide, silica, alumina
and cobalt results in a sorbent which permits the removal of
thiophenic sulfur compounds from fluid streams of cracked-gasolines
or diesel fuels without having a significant adverse affect of the
olefin content of such streams, thus avoiding a significant
reduction of octane values of the treated stream. Moreover, the use
of such novel sorbents results in a significant reduction of the
sulfur content of the resulting treated fluid stream.
[0029] In a presently preferred embodiment of this invention, the
sorbent composition has a cobalt content in the range of from about
5 to about 50 weight percent.
[0030] The zinc oxide used in the preparation of the sorbent
composition can either be in the form of zinc oxide, or in the form
of one or more zinc compounds that are convertible to zinc oxide
under the conditions of preparation described herein. Examples of
such zinc compounds include, but are not limited to, zinc sulfide,
zinc sulfate, zinc hydroxide, zinc carbonate, zinc acetate, and
zinc nitrate. Preferably, the zinc oxide is in the form of powdered
zinc oxide.
[0031] The silica used in the preparation of the sorbent
compositions may be either in the form of silica or in the form of
one or more silicon-containing compounds. Any suitable type of
silica maybe employed in the sorbent compositions of the present
invention. Examples of suitable types of silica include diatomite,
silicalite, silica colloid, flame-hydrolyzed silica, hydrolyzed
silica, silica gel and precipitated silica, with diatomite being
presently preferred. In addition, silicon compounds that are
convertible to silica such as silicic acid, sodium silicate and
ammonium silicate can also be employed. Preferably, the silica is
in the form of diatomite.
[0032] The starting alumina component of the composition can be any
suitable commercially available alumina material including
colloidal alumina solutions and, generally, those alumina compounds
produced by the dehydration of alumina hydrates.
[0033] The zinc oxide will generally be present in the sorbent
composition in an amount in the range of from about 10 weight
percent to about 90 weight percent, and preferably in an amount in
the range of from about 15 to about 60 weight percent when such
weight percents are expressed in terms of the zinc oxide based upon
the total weight of the sorbent composition.
[0034] The silica will generally be present in the sorbent
composition in an amount in the range of from about 5 weight
percent to about 85 weight percent, preferably in an amount in the
range of from about 20 weight percent to about 60 weight percent
when the weight percents are expressed in terms of the silica based
upon the total weight of the sorbent composition.
[0035] The alumina will generally be present in the sorbent
composition in an amount in the range of from about 5.0 weight
percent to about 30 weight percent, preferably from about 5.0
weight percent to about 15 weight percent when such weight percents
are expressed in terms of the weight of the alumina compared with
the total weight of the sorbent system.
[0036] In the manufacture of the sorbent composition, the primary
components of zinc oxide, silica and alumina are combined together
in appropriate proportions by any suitable manner which provides
for the intimate mixing of the components to provide a
substantially homogeneous mixture.
[0037] Any suitable means for mixing the sorbent components can be
used to achieve the desired dispersion of the materials. Such means
include, among others, tumblers, stationary shells or troughs,
Muller mixers, which are of the batch or continuous type, impact
mixers and the like. It is presently preferred to use a Muller
mixer in the mixing of the silica, alumina and zinc oxide
components.
[0038] Once the sorbent components are properly mixed to provide a
shapeable mixture, the resulting mixture can be in the form of wet
mix, dough, paste or slurry. If the resulting mix is in the form of
a wet mix, the wet mix can be densified and thereafter particulated
through the granulation of the densified mix following the drying
and calcination of same. When the admixture of zinc oxide, silica
and alumina results in a form of the mixture which is either in a
dough state or paste state, the mix can be shaped to form a
particulate granule, extrudate, tablet, sphere, pellet or
microsphere. Presently preferred are cylindrical exrudates having
from {fraction (1/32)} inch to 1/2 inch diameter and any suitable
length. The resulting particulate is then dried and then calcined.
When the mix is in the form of a slurry, the particulation of same
is achieved by spray drying the slurry to form micro-spheres
thereof having a size of from about 20 to about 500 microns. Such
microspheres are then subjected to drying and calcination.
Following the drying and calcination of the particulated mixture,
the resulting particulates can be impregnated with cobalt oxide
compound or a cobalt oxide precursor.
[0039] Following the impregnation of the particulate compositions
with the appropriate cobalt compound, the resulting impregnated
particulate is then subjected to drying and calcination prior to
the subjecting of the calcined particulate to reduction with a
reducing agent, preferably hydrogen.
[0040] The elemental cobalt, cobalt oxide or cobalt-containing
compound can be added to the particulated mixture by impregnation
of the mixture with a solution, either aqueous or organic, that
contains the elemental cobalt, cobalt oxide or cobalt-containing
compound. In general, the impregnation with the cobalt is carried
out so as to form a resulting particulate composition of zinc
oxide, silica, alumina and the cobalt metal, cobalt oxide or cobalt
oxide precursor prior to the drying and calcination of the
resulting impregnated composition.
[0041] The impregnation solution is any aqueous solution and
amounts of such solution which suitably provides for the
impregnation of the mixture of zinc oxide, silica and alumina to
give an amount of cobalt oxide in the final zinc oxide based
composition to provide when reduced a reduced cobalt metal content
sufficient to permit the removal of sulfur from streams of
cracked-gasoline or diesel fuels when so treated with same in
accordance with the process of the present invention.
[0042] Once the cobalt, cobalt oxide or cobalt oxide precursor has
been incorporated into the particulate calcined zinc oxide, alumina
and silica mixture, the desired reduced valence cobalt metal
sorbent is prepared by drying the resulting composition followed by
calcination and thereafter subjecting the resulting calcined
composition to reduction with a suitable reducing agent, preferably
hydrogen, so as to produce a composition having a substantial zero
valence cobalt content therein with such zero valence cobalt
content being present in an amount to permit the removal with same
of sulfur from a cracked-gasoline or diesel fuel fluid stream.
[0043] The solid reduced cobalt metal sorbent of this invention is
a composition that has the ability to react with and/or chemisorb
with organo-sulfur compounds, such as thiophenic compounds. It is
also preferable that the sorbent removes diolefins and other gum
forming compounds from the cracked-gasoline.
[0044] The solid reduced metal sorbent of this invention is
comprised of cobalt that is in a substantially reduced valence
state, preferably a zero valence state. Presently the reduced metal
is cobalt. The amount of reduced cobalt in the solid cobalt reduced
metal sorbents of this invention is that amount which will permit
the removal of sulfur from a cracked-gasoline or diesel fuel fluid
stream. Such amounts are generally in the range of from about 5 to
about 50 weight percent of the total weight of cobalt in the
sorbent composition. Presently it is preferred that the reduced
cobalt metal be present in an amount in the range of from about 15
to about 40 weight percent of the total weight of cobalt in the
sorbent composition.
[0045] In one presently preferred embodiment of the present
invention, the reduced cobalt is present in an amount in the range
of from about 15 to 30 weight percent and the cobalt component has
been substantially reduced to zero valence.
[0046] In another presently preferred embodiment of this invention,
zinc oxide is present in an amount of about 38 weight percent,
silica is present in an amount of about 31 weight percent, alumina
is present in an amount of about 8 weight percent and cobalt is
present prior to reduction to zero valence in an amount of about 33
weight percent cobalt oxide.
[0047] From the above, it can be appreciated that the sorbent
compositions which are useful in the desulfurization process of
this invention can be prepared by a process which comprises:
[0048] (a) admixing zinc oxide, silica and alumina so as to form a
mix of same in the form of one of a wet mix, dough, paste or
slurry;
[0049] (b) particulating the resulting mix to form particulates
thereof in the form of one of granules, extrudates, tablets,
pellets, spheres or microspheres;
[0050] (c ) drying the resulting particulate;
[0051] (d) calcining the dried particulate;
[0052] (e) impregnating the resulting calcined particulate with
cobalt, cobalt oxide or a precursor for cobalt;
[0053] ( f ) drying the impregnated particulate;
[0054] (g) calcining the resulting dried particulate; and
[0055] (h) reducing the calcined particulate product of (g) with a
suitable reducing agent so as to produce a particulate composition
having a substantial reduced valence cobalt content therein and
wherein the reduced valence cobalt content is present in an amount
sufficient to permit the removal with same of sulfur from a
cracked-gasoline or diesel fuel fluid stream when contacted with
the resulting substantially reduced valence cobalt particulated
sorbent.
[0056] The process to use the novel sorbents to desulfurized
cracked-gasoline or diesel fuels to provide a desulfurized
cracked-gasoline or diesel fuel comprises:
[0057] (a) desulfurizing in a desulfurization zone a
cracked-gasoline or diesel fuel with a solid reduced cobalt
metal-containing sorbent;
[0058] (b) separating the desulfurized cracked-gasoline or
desulfurized diesel fuel from the resulting sulfurized solid
reduced cobalt-containing sorbent;
[0059] (c ) regenerating at least a portion of the sulfurized solid
reduced cobalt-containing sorbent to produce a regenerated
desulfurized solid cobalt-containing sorbent;
[0060] (d) reducing at least a portion of the regenerated
desulfurized solid cobalt-containing sorbent to produce a solid
reduced cobalt-containing sorbent thereafter and;
[0061] (e) returning at least a portion of the regenerated solid
reduced cobalt-containing sorbent to the desulfurization zone.
[0062] The desulfurization step (a) of the present invention is
carried out under a set of conditions that includes total pressure,
temperature, weight hourly space velocity and hydrogen flow. These
conditions are such that the solid reduced cobalt-containing
sorbent can desulfurized the cracked-gasoline or diesel fuel to
produce a desulfurized cracked-gasoline or desulfurized diesel fuel
and a sulfurized sorbent.
[0063] In carrying out the desulfurization step of the process of
the present invention, it is preferred that the feed
cracked-gasoline or diesel fuel be in a vapor phase. However, in
the practice of the invention it is not essential, albeit
preferred, that the feed be totally in a vapor or gaseous
state.
[0064] The total pressure can be in the range of about 15 psia to
about 1500 psia. However, it is presently preferred that the total
pressure be in a range of from about 50 psia to about 500 psia.
[0065] In general, the temperature should be sufficient to keep the
cracked-gasoline or diesel fuel essentially in a vapor phase. While
such temperatures can be in the range of from about 100.degree. F.
to about 1000.degree. F., it is presently preferred that the
temperature be in the range of from about 400.degree. F. to about
800.degree. F. when treating as cracked-gasoline and in the range
of from about 500.degree. F. to about 900.degree. F. when the feed
is a diesel fuel.
[0066] Weight hourly space velocity (WHSV) is defined as the pounds
of hydrocarbon feed per pound of sorbent in the desulfurization
zone per hour. In the practice of the present invention, such WHSV
should be in the range of from about 0.5 to about 50, preferably
about 1 to about 20 hr.sup.-1.
[0067] In carrying out the desulfurization step, it is presently
preferred that an agent be employed which interferes with any
possible chemisorbing or reacting of the olefinic and aromatic
compounds in the fluids which are being treated with the solid
reduced cobalt-containing sorbent. Such an agent is presently
preferred to be hydrogen.
[0068] Hydrogen flow in the desulfurization zone is generally such
that the mole ratio of hydrogen to hydrocarbon feed is the range of
about 0.1 to about 10, and preferably in the range of about 0.2 to
about 3.0.
[0069] The desulfurization zone can be any zone wherein
desulfurization of the feed cracked-gasoline or diesel fuel can
take place. Examples of suitable zones are fixed bed reactors,
moving bed reactors, fluidized bed reactors and transport reactors.
Presently, a fluidized bed reactor or a fixed bed reactor is
preferred.
[0070] If desired, during the desulfurization of the vaporized
fluids, diluents such as methane, carbon dioxide, flue gas, and
nitrogen can be used. Thus it is not essential to the practice of
the process of the present invention that a high purity hydrogen be
employed in achieving the desired desulfurization of the
cracked-gasoline or diesel fuel.
[0071] It is presently preferred when utilizing a fluidized system
that a solid reduced cobalt sorbent be used that has a particle
size in the range of about 20 to about 1000 micrometers.
Preferably, such sorbents should have a particle size of from about
40 to about 500 micrometers. When a fixed bed system is employed
for the practice of the desulfurization process of this invention,
the sorbent should be such as to have a particle size in the range
of about {fraction (1/32)} inch to about 1/2 inch diameter.
[0072] It is further presently preferred to use solid reduced
cobalt sorbents that have a surface area of from about 1 square
meter per gram to about 1000 square meters per gram of solid
sorbent.
[0073] The separation of the gaseous or vaporized desulfurized
fluids and sulfurized sorbent can be accomplished by any means
known in the art that can separate a solid from a gas. Examples of
such means are cyclonic devices, settling chambers or other
impingement devices for separating solids and gases. The
desulfurized gaseous cracked-gasoline or desulfurized diesel fuel
can then be recovered and preferably liquefied.
[0074] The gaseous cracked-gasoline or gaseous diesel fuel is a
composition that contains in part, olefins, aromatics and
sulfur-containing compounds as well as paraffins and
naphthenes.
[0075] The amount of olefins in gaseous cracked-gasoline is
generally in the range of from about 10 to 35 weight percent based
on the weight of the gaseous cracked-gasoline. For diesel fuel
there is essentially no olefin content.
[0076] The amount of aromatics in gaseous cracked-gasoline is
generally in the range of about 20 to about 40 weight percent based
on the weight of the gaseous cracked gasoline. The amount of
aromatics in gaseous diesel fuel is generally in the range of about
10 to about 90 weight percent.
[0077] The amount of sulfur in cracked-gasolines or diesel fuels
can range from about 100 parts per million sulfur by weight of the
gaseous cracked-gasoline to about 10,000 parts per million sulfur
by weight of the gaseous cracked-gasoline and from about 100 parts
per million to about 50,000 parts per million for diesel fuel prior
to the treatment of such fluids with the sorbent system of the
present invention.
[0078] The amount of sulfur in cracked-gasolines or in diesel fuels
following treatment of same in accordance with the desulfurization
process of this invention is less than 100 parts per million.
[0079] In carrying out the process of this invention, if desired, a
stripper unit can be inserted before the regenerator for
regeneration of the sulfurized sorbent which will serve to remove a
portion, preferably all, of any hydrocarbons from the sulfurized
sorbent or before the hydrogen reduction zone so as to remove
oxygen and sulfur dioxide from the system prior to introduction of
the regenerated sorbent into the sorbent activation zone. The
stripping comprises a set of conditions that includes total
pressure, temperature and stripping agent partial pressure.
[0080] Preferably the total pressure in a stripper, when employed,
is in a range of from about 25 psia to about 500 psia.
[0081] The temperature for such strippers can be in the range of
from about 100.degree. F. to about 1000.degree. F.
[0082] The stripping agent is a composition that helps to remove
hydrocarbons from the sulfurized solid sorbent. Presently, the
preferred stripping agent is nitrogen.
[0083] The sorbent regeneration zone employs a set of conditions
such that at least a portion of the sulfurized sorbent is
desulfurized.
[0084] The total pressure in the regeneration zone is generally in
the range of from about 10 to about 1500 psia. Presently preferred
is a total pressure in the range of from about 25 psia to about 500
psia.
[0085] The sulfur removing agent partial pressure is generally in
the range of from about 1 percent to about 25 percent of the total
pressure.
[0086] The sulfur removing agent is a composition that helps to
generate gaseous sulfur oxygen-containing compounds such a sulfur
dioxide, as well as to burn off any remaining hydrocarbon deposits
that might be present. Currently, oxygen-containing gases such as
air are the preferred sulfur removing agent.
[0087] The temperature in the regeneration zone is generally from
about 100.degree. F. to about 1500.degree. F. with a temperature in
the range of about 800.degree. F. to about 1200.degree. F. being
presently preferred.
[0088] The regeneration zone can be any vessel wherein the
desulfurizing or regeneration of the sulfurized sorbent can take
place.
[0089] The desulfurized sorbent is then reduced in an activation
zone with a reducing agent so that at least a portion of the cobalt
content of the sorbent composition is reduced to produce a solid
cobalt reduced metal sorbent having an amount of reduced metal
therein to permit the removal of sulfur components from a stream of
cracked-gasoline or diesel fuel.
[0090] In general, when practicing the process of this invention,
the reduction of the desulfurized solid cobalt-containing sorbent
is carried out at a temperature in the range of about 100.degree.
F. to about 1500.degree. F. and a pressure in the range of about 15
to 1500 psia. Such reduction is carried out for a time sufficient
to achieve the desired level of cobalt reduction in the sorbent
system. Such reduction can generally be achieved in a period of
from about 0.01 to about 20 hours.
[0091] Following the activation of the regenerated particulate
sorbent, at least a portion of the resulting activated (reduced)
sorbent can be returned to the desulfurization unit.
[0092] When carrying out the process of the present invention in a
fixed bed system, the steps of desulfurization, regeneration,
stripping, and activation are accomplished in a single zone or
vessel.
[0093] The desulfurized cracked-gasoline resulting from the
practice of the present invention can be used in the formulation of
gasoline blends to provide gasoline products suitable for
commercial consumption.
[0094] The desulfurized diesel fuels resulting from the practice of
the present invention can likewise be used for commercial
consumption where a low sulfur-containing fuel is desired.
EXAMPLES
[0095] The following examples are intended to be illustrative of
the present invention and to teach one of ordinary skill in the art
to make and use the invention. These examples are not intended to
limit the invention in any way.
Example I
[0096] A solid reduced cobalt metal sorbent was produced by dry
mixing 20.02 pounds of diatomite silica and 25.03 zinc oxide in a
mix Muller for 15 minutres to produce a first mixture. While still
mixing, a solution containing 6.38 pounds of Disperal alumina
(Condea), 22.5 pounds of deionized water and 316 grams of glacial
acetic acid were added to the mix Muller to produce a second
mixture. After adding these components, mixing continued for an
additional 30 minutes. This second mixture was then dried at
300.degree. F. for 16 hours and then calcined at 1175.degree. F.
for one hour to form a third mixture. This third mixture was then
particularized by granulation using a Stokes Pennwalt granulator
fitted with a 50 mesh screen. 200 grams of the resulting granulated
mix was then impregnated with 148 grams of cobalt nitrate
hexahydrate dissolved in 43 grams of hot (200.degree. F.) deionized
water to produce a particulate impregnated mix. The impregnated
particulate was dried at 300.degree. F. for one hour and then
calcined at 1175.degree. F. for one hour. 100 grams of the calcined
particulate was impregnated with a solution of 74 grams of cobalt
nitrate hexahydrate dissolved in 8 grams of hot deionized water to
produce an impregnated particulate product which was then dried at
300.degree. F. for one hour and then calcined at 1175.degree. F.
for one hour to form a solid cobalt oxide sorbent.
[0097] The solid cobalt oxide sorbent was then reduced by
subjecting it to a temperature of 700.degree. F., a total pressure
of 15 psia and a hydrogen partial pressure of 15 psi for 30 minutes
to produce a solid reduced cobalt sorbent wherein the cobalt
component of the sorbent composition was substantially reduced to a
zero valence state.
Example II
[0098] The solid reduced cobalt sorbent as prepared in Example I
was tested for its desulfurization ability as follows.
[0099] A one inch quartz reactor tube was loaded with the indicated
amounts of the sorbent of Example I. This solid reduced cobalt
sorbent was placed on a frit in the middle of the reactor. Gaseous
cracked-gasoline having about 345 parts per million sulfur by
weight of the sulfur-containing compounds based on the weight of
the gaseous cracked-gasoline and having about 95 weight percent
thiophenic compounds (such as for example, alkyl benzothiphenes,
alkyl thiophenes, benzothiophene and thiophene) based on the weight
of sulfur-containing compounds in the gaseous cracked-gasoline was
pumped upwardly through the reactor. The rate was 13.4 milliliters
per hour. This produced sulfurized solid sorbent and desulfurized
gaseous cracked-gasoline.
[0100] In Run 1, hydrogen was added to the gasoline feed at a
partial pressure of 6.6 psi (out of a total pressure of 15 psi)
resulting in a reduction in gasoline sulfur to 15-25 parts per
million.
[0101] After Run 1, the sulfurized sorbent was subjected to
regeneration conditions that included a temperature of 900.degree.
F., a total pressure of 15 psia and an oxygen partial pressure of
0.6 to 3.1 psi for a period of 1-2 hours. Such conditions are
hereinafter referred to as "regeneration conditions" to produce a
desulfurized cobalt-containing sorbent. This sorbent was then
subjected to reducing conditions that included a temperature of
700.degree. F., a total pressure of 15 psia and a hydrogen partial
pressure of 15 psi for a time period of 0.5 hours. Such conditions
are hereinafter referred to as "reducing conditions".
[0102] In the next series of runs (2-6), after each run the
sulfurized sorbent was subjected to regeneration and reducing
conditions as described above.
[0103] Runs 2 and 3 were essentially repeats of Run 1 indicating
that the sorbent can be regenerated to a fresh state where it can
reduce the sulfur content of cracked-gasoline to about 5 parts per
million.
[0104] A composite of product gasoline from each of the Runs 1 and
2 was subjected to a test to determine its research octane number
(RON), using a method as described in ASTM 2699 procedure entitled
"Research Octane Number of Sparked Ignition Engine Fuel". The RON
for the products from Runs 1 and 2 was 91.4 as compared to the RON
of 91.1 for the cracked-gasoline feed, indicating that the octane
of the cracked-gasoline was not affected by carrying out the
inventive desulfurization process.
[0105] In Runs 4-7, the effect of hydrogen partial pressure was
studied. As the hydrogen partial pressure is reduced (Run 4), the
ability of the sorbent to desulfurized cracked-gasoline diminished.
When no hdyrogen is used in the process (Run 5), very little
reduction in the sulfur content is effected. When the hydrogen
partial pressure was increased to 13.2, the sorbent essentially
reduced the cracked-gasoline to less than 5 parts per million.
[0106] Run 7 was a repeat of Runs 1-3 and indicates that even after
repeated cycles of desulfurization, regeneration and reduction or
activation, the ability of the sorbent to remove sulfur from
cracked gasoline did not diminish, for example compare Run 1 to Run
7.
[0107] The results of this series of runs is set forth in Table
1.
1TABLE 1 Reactor Run Number Conditions 1 2 3 4 5 6 7 Amount 10 10
10 10 10 10 10 (grams) TP.sup.1 15 15 15 15 15 15 15 HPP.sup.2 6.6
6.6 6.6 2.25 0 13.2 6.6 .degree. F. 700 700 700 700 700 700 700
TOS.sup.3 Sulfur.sup.4 1 15 5 5 75 285 5 15 2 20 5 <5 105 385
<5 15 3 25 5 <5 110 320 <5 10 4 25 5 115 <5 5 5 24 10
<5 10 RON 91.4 91.4 .sup.1Total pressure in psia. .sup.2Hydrogen
particla pressure in psia. .sup.3The time on stream in hours.
.sup.4The amount of sulfur-containing compounds left in the
desulfurized cracked-gasoline in parts per million sulfur by weight
based on the weight of the desulfurized cracked-gasoline.
[0108] The specific examples herein disclosed are to be considered
as being primarily illustrative. Various changes beyond those
described will no doubt occur to those skilled in the art; and such
changes are to be understood as forming a part of this invention
insofar as they fall within the spirit and scope of the appended
claims.
* * * * *