Note: Descriptions are shown in the official language in which they were submitted.
The present invention relates to catalysts whic~
are used to catalytically crack hydrocarbons and to
sulfur oxide absorbing/gettering a~ent compo~itions
which may be used to control sulfur oxide emissions.
More specifically, the invention contemplates the
preparation and use of catalytic cracking catalysts
which are cap~ble of reducing the amount of sulfur
oxides (SOx~ emitted to the atmosphere during
regeneration of the catalyst, and to highly eficient
1~ Sx control agents which may be used to control
Sx emissions from a variety of processes.
Cracking catalysts which are used ~o crack
hydrocarbon feedstocks become relatively inactive due
to the deposition of carbonaceous deposits on the
catalyst. These carbonaceous deposits are commonly
called ~okeO When the feedstocks contain organic
sulfur compounds, the coke on the catalyst contains
sulfur. After the cracking step, the catalyst passes
to a stripping zone where steam is used to remove
strippable hydrocarbons from the catalyst. The
catalyst then yoes to the regenerator, where the
catalyst is regeneratd by burning the coke in an
oxygen-containing gas. This converts the carbon an~
hydrogen in the coke to carbon monoxide, carbon
dioxide and water. The sulfur in the coke is
converted to oxides of sulfur, SO2 and SO3, i.e.
SOX .
Generally, the greater the amount of sulfur in the
feedstock, the greater the amount of sulfur in the
coke. Likewise, the greater the amount of sulfur in
the coke, the greater the amount of sulfur oxides in
the flue gas exiting from the regenerator. In
--2--
qeneral, the amount of SO2 and SO3, i.e. SOx, in
the flue gas amounts to about 250 to 2,500 parts per
milllon by volume.
- The prior art has suggested various methods for
S removing or preventing the liberation oE SO~ to the
atmosphere during oxidative combustion of sulfur
containing fuels~residues. Typically, FCC/combustion
units have been equipped with conventional scrubbers
in which the Sx components are removed from flue
gas by absorption/reaction with gettering agents
(sometimes referred to as ''Sx acceptors") such as
calcium oxide. In some instances, hydrocarbon
feedstocks are pretreated (hydrotreated) to remove
sulfur. It has also been claimed that sulfur oxide
emissions from FCC units may be controlled by use of a
cracking catalyst in combination with a sulfur
absorber or gettering agent. It has also been claimed
that these sulfur gettering agents are more effective
when used in the presence of oxidation catalysts.
Oxidation catalysts are currently being used in
FCC units to oxidize CO to CO2 in the catalys~ bed
during the coke burning step in the regenerator. The
oxidation of CO to CO2 in the catalyst bed yields
many benefits. One benefit is the reduction of CO
emissions. Another is the avoidance of
"after-burning", i.e., the oxidation of CO to CO~
outside the catalyst bed, which results in a loss of
heat energy and causes damage to the cyclones and flue
gas exit lines. The major benefit in using oxidation
catalysts to oxidize CO to CO2 in the catalyst
regenerator bed derives from the heat released when
the CO is oxidized to CO2. This heat raises the
catalyst bed temperature and thereby increases the
--3~
coke-burning rate. This gives a lower residual carhon
level on regenerated catalyst (CRC). This, in turn,
makes the regenerated catalyst more active for the
cracking step. This increases the amount of useful
products produced in the FCC unit.
In view of the act that CO oxidation catalysts
are currently being used in many FCC units for
economic reasons, Sx gettering agents for use in
FCC units must be compatihle and efective in the
presence o oxidation catalysts. Furthermore, Sx
gettering agents for use in FCC units must be
effective under the actual conditions seen in FCC
units, such as temperatures of 800-1000F and catalyst
residence times of 3 to 15 seconds in the reducing
atmosphere of the reactor, temperatures of 800-1000F
in the steam atmosphere of the stripper, temperatures
of 1100-1400F and catalyst residence times of 5 ~o 15
minutes in the oxidizing atmosphere oE the
regenerator~ Additionally, Sx gettering agents for
use in FCC units must be effective in the presence of
the materials present in FCC units, such as cracking
catalysts of various compositions, oil feedstocks of
various compositions and their cracked products, and,
as stated earlier~ oxidation catalysts to oxidize CO
to CO2.
\
--4--
ii 5
The ollowing U.S. patents disclose the use of
cracking catalysts which contain various sulfur and
carhon monoxide emission control agents.
- 3,542,670
3,699,037
3,~35,031
4,071,436
~,115,249
4,115,250
4,115,251
4,137,151
~,151,119
4,15~,298
4,153,53~
4,153p535
4,1~6,787
~,182,693
4,187,199
4,2~0,520
4,206,039
4,206,085
4,221,677
4,238,317
As shown in the above noted reerences, organic
sulfur present during regeneration of the cracking
catalyst is ultimately oxidized to sul~ur triox.ide
(SO3~ which reacts with a gettering agent to form a
stable sulfate which is retained in the catalyst
inventory of the FCC unit. Regenerated catalyst
containing the sulfate compound is recycled to the
cracking zone where the catalyst is mixed with oil and
steam dispersant to effect the cracking reaction and
conversion of the oil to useful products (gasoline,
light olefins, etc~).
When the sulfate-containing catalyst is exposed to
the reducing and hydrolyzing conditions present during
the cracking step and the suhsequent hydrolyæing
conditions present in the steam stripper, the sulfate
is reduced and h~drolyzed to orm hydroqen sulfide
(H2S) and restore or regenerate the qettering
agent. The hydrogen sulfide is recovered as a
component of the cracked product stream. ~he
gettering agent is re-cycled to the regenerator to
repeat the process. Through use of catalysts
containing appropriate gettering agent6, it is
disclosed that the amount of sulfur oxides emitted
1~ from the regenerator may be significantly reduced.
However, it has been found that attempts to
produce SOx-control cracking catalysts which can
consistently achieve significant sulfur oxide emission
reduction over long periods of time have in general
been unsuccessful.
Accordingly, it is an ob~ect of the present
invention to provide a cracking catalyst composition
which effectively and economically reduces the
emission of sulfur oxides ~rom FCC units.
It is another object to provide a sulfur oxide
gettering agent which is capable of removing sulfur
oxiaes over a long period of time when subjected to
multiple gettering/regeneration cycles.
It is a further object to provide a Sx control
additive which may be added to the catalyst inventory
of an FCC unit in amounts necessary to reduce sulfur
oxide regenerator stack gas emissions ~o an acceptable
level.
It is still a further object to provide highly
effective sulfur oxide gettering agen~s which may be
advantageously combined with conventional cracking
~atalyst compositions or used to control Sx
emissions from a variety of proces~es.
These and still further objects will become
apparent to one skilled in the art from the following
detailed description, specific examples and drawing
wherein the Figure is a graphical representation of
data which illu~trates Sx Index vs. La2O3
content of Sx gettering agents of the present
invention.
Broadly~ our invention contemplates catalytic
cracking catalyst compositions which include an
alumina-lanthanum oxide Sx gettering agent.
Furthermore, our invention contemplates an improved
Sx gettering agent which comprises sn alumina
(A12O3) substrate coated with lanthanum oxide
(La2O3) in amounts which provide approximately a
theoretical mono-layer of La2O3 molecules on the
surface of the alumina substrate~ These gettering
agents may be effectively combined with or included in
particulate catalyst compositions used for the
catalytic cracking of hydrocarbons, or alternatively
the gettering agents may be used in any combustion
process which generates Sx components that are to
be selectively removed from the combustion products.
More specifically, we have foun~ that a
particularly effective Sx absorber/gettering agent
suitable for use with catalytic cracking catalyst may
be obtained by combining the soluble lanthanum salt
solution with a porous alumina substrate in amounts
which will distribute upon the sllrface of the alumina
substrate a layer of lanthanum oxide approximately one
molecule in thickness.
In practice, we find that the desired result is
achieved with about 5 to 50 percent by weight
La2O3 combined with an alumina substra~e which has
a surace area of rom ahout 45 to ~50 m2/g;
preerably, about 12 to 30 percent by weight La2O3
com~ined with an alumina substrate which has a surface
area oE about 110 to 270 m2/g; and more preferably
about 20 percent by weight La2O3 combined with an
alumina substrate which has a surface area of about
180 m2/g.
Suitable alumina substrates are available from
many commercial sources, and comprise the alumina
hydrates, such as alpha alumina monohydrate~ alpha
lS alumina trihydrate, beta alumina monohydrate and beta
alumina trihydrate. Also considered most suitable are
the calcined versions of the above alumina hydrates~
These include gamma alumina, chi alumina, eta alumina,
kappa alumina~ delta alumina, theta alumina t alpha
alumina and mixtures thereof.
The lanthanum oxide component which is distended
upon the alumina surface may be obtained as a
commercially avalilable lanthanum salt such as
lanthanum nitrate or chloride or sulfate, or
alternatively, a mixed rare earth salt which contain~
other rare earth elements such as Nd, Ce, Pr and Sm
may be utilized. The rare earth component of a
typical commercially available mixed rare earth salt
solution which includes lanthanum has the followin~
approxlmate composi~ion, expressed as oxides: 60%
La~O3, 20% Nd2O3, 14% CeO2, 5% Pr6Oll
and 1~ Sm2O3. It should be understood that in the
event a mixed rare earth salt source is utilized the
quantity of mixed rare earth salts used should ~e
sufficient to provide the desired level of La203
on the alumina substrate.
The amount of lanthanum oxide utilized in the
preparation of the novel Sx gettering agent is
preferably that quantity which will provide a
mono-layer of lanthanum oxide molecules over the
sur~ace of the a~umina substrate. In the event the
quantity of lanthanum oxide, as specified above, is
substantially exceeded, i.e., multi-layer or bulk
lanthanum oxide is formed, and the efectiveness of
1~ the Sx gettering agent is adversely affected. On
the other hand~ if insufficient lanthanum oxide is
used, the effectiveness of the gettering agent i~ less
than it could be.
While the precise mechanism is not fully
understood, it is believed that the active specie is a
La203 molecule fixed on the alumina surface in
some sort of a surface complex of La203 and
A1~03. This surface La203 on A1~03
complex is very reactive in sombining with su~ur
oxides to form a thermally stahle solid sulfate or
sulfate-type compound. Furthermore t this thermally
stable solid sulfate or sulfate-type compound can be
easily reduced-hydrolyzed to produce volatile hydroqen
sulfide and restore or regenerate the original surface
25 La203 on A1203 comple~. The hydrogen sulfide
can be recovered as a component of the product
stream. The restored or regenerated gettering agent
can be recycled to repeat the absorption and
regeneration steps.
~o prepare our novel Sx gettering agent9 ~he
alumina substrate is~uniforJDly and thoroughly admixed
with a quantity of lanthanum salt solution which will
provide the desired uniform dispersion of lanthanum
oxide on the surface. Typically, the sol~lble
lanthanum salt, preferably lanthanum nitrate, is
dissolved in water to provide a desired volume of
solution which has the desired concentration of the
lanthanum salt. The alumina substrate is then
impregnated, as uniformly as possible, with the
lanthanum salt solution to give the desired amount of
lanthanum on the alumina. The impregnated alumina is
then calcined at a temperature sufficient to decompose
the lanthanum salt and fix the resulting lanthanum
oxide uniEormly onto the alumina surface. While it is
contemplated that calcination temperatures of up to
about 1500F may be used, calcination temperatures on
the order of 1000F have been found to be satisEactory.
In one preferred embodiment of the invention, the
alumina substrate to be impregnated is in the form o~
microspheroidal particles, with about 90% of the
particles having diameters in the 20 to 149 micron
fluidiæable size range. The gettering agent ~repared
using these microspheroidal particles may be
advantageously physically mixed with FCC catalysts in
amounts ranging from about 0.5 to 60 percent by weight
of the overall composition.
In another preferred embodiment of the invention,
the alumina substrate to be impregnated is in the form
of particles which have an average particle ~i~e of
less than 20 microns in diameter, and preferably less
than 10 microns in diameter. The finished gettering
agen~: prepared using these fine particles may ~e
incorporated in a crackinq catalyst composition d~ring
the formation of the catalyst particles.
--10--
Typically, the lanthanum impregnated alumina is
added to an aqueous slurry of catalyst components
prior to forming, i.e. spray drying in the case of FCC
catalysts.
In another em~odiment of the in~ention, the
alumina substrate to be impregnated is in the form of
particles one millimeter or greater in diameter. The
finished gettering agent prepared using these
particles can be used in either a fixed-bed or
moving-bed configuration to reduce Sx emissions
from a variety o processes.
Therefore, it is seen that the present gettering
agent may be used as a separate additive whicll is
added to the catalyst as a separate particulate
component, or the gettering agent may be combined with
the catalyst during its preparation to obtain catalys~
particles which contain the gettering agent as an
integral component. Aclclitionally, the gettering agent
may be used by itself to reduce Sx emissions from a
variety of processes.
Cracking catalysts which may be advantageously
combined with the SOy gettering agent of the present
invention are commercially ava;lable compositions and
typically cornprise crystalline zeolites admixed with
inorganic oxide binders and clay. Typically, these
catalysts comprise from about 5 to 50 percent by
weight crystalline aluminosilicate zeolite in
combination with a silica, silica-alumina, or alumina
hydrogel or sol binder and optionally from about 10 to
~0 percent by weight clay. ~eolites typicallv used in
the preparation of cracking catalysts are stabilized
type Y zeolites the preparation of which is dlsclosed
in U.S. 3,293,192, 3,375,065, 3,402,996, 3,449,070 and
3,595,611. Preparation of catalyst compositions which
-11-
may be used in the practice of our invention are
typically disclosed in U.S. patents 3,957,689,
3,867,308~ 3,912,611 and ~anadian 967,136.
-In a preferred practice of the inventiorl, the
cracking catalyst get~ering composition will be used
in combination with a noble metal oxidation catalyst
such as platinum and/or palladium.
In another preferred practice of the inventionr
the Sx getteriny agent is combined with a cracking
catalyst which comprises an alumina sol, i e. aluminum
chlorhydroxide solu-tion, bound zeolite/clay
composition as disclosed in Canadian Patent 967,136
admixed with a particulate platinum containing
oxidation catalyst to obtain a composition which
comprlses 0.5 to 60 percent by weight gettering agent,
40 to 99 percent by weight cracking catalyst, and 1 to
5 parts per million platinum.
In still another preferred practice of the
invention, the Sx gettering agent is combined with
a zeolite cracking catalyst which possesses an
essentially sllica-free matrix. These catalysts are
obtained by using the procedure set forth in Canadian
9~7,136 by mixing together the following materials: 5
to 50 weight percent zeolite, 10 to 80 weight percent
alumina hydrate (dry basis), and 5 to 40 weight
percent aluminum chIorhydroxide sol ~A12O3~, and
water. The mixture was spray-dried to obtain a finely
divided catalyst composite ancl then calcined at a
temperature oE about 1000F. The Sx gettering
agent may be included as a component in the spray
dried slurry in lieu of some of the alumina hydrate or
the ~G~ gettering agent may be vhysically ~lend~d
with the catalyst in the amount of about 0.5 to 60
weight percent.
-12-
As indicated above, the getterinq agent may be
utilized in the form of a separate particulate
additive which is physically blended with a
particulate catalyst or the gettering agent may be
incorporated in the catalyst particle by admixing the
additive with the catalyst components prior to forming
of the catalyst. In addition it is contemplated that
the gettering agent may be utilized in any
combustion/reaction process where it is desirable to
collect or remove sulfur oxides from a product gas
stream. Typicallyr the Sx gettering agent may be
used in a fluidizPd coal combustion process to remove
Sx formed during burning of the coal. ~he Sx
get~ering agent may then be removed from the
combustion/reaction 20ne periodically or continuously
to restore or regenerate the gettering agent by
subjecting it to reduction-hydrolysis in the presence
of hydrogen or carbon monoxide-hydrogen reducing gas
mixtures (i.e. syn-gas) and H20. Using this
technique, the Sx component of the combustion
products is selectively removed as a stable sulfate,
and the sulfate is subsequently reduced-hydroly2ed to
liberate H2S and restore or regenerate the gettering
agent. The H~S may be recovered using conventional
adsorbing techniques.
~ aving described the basic aspects of our
invention, the fo:Llowing examples are given to
illustrate specific embodiments thereof.
-13-
EXAMPLE 1
A solution o~ lanthanum nitrate was prepared by
dissolving 79.7 g of lanthanum nitrate,
La(NO3)3.6H2O, in a sufficient amount of water
to give 100 ml of solution. 10 ml of this solution
contains 3.0 g of lanthanum expressed as lanthanum
oxide, La203.
EXAMPLE 2
3608 g (27 g dry basis) of a commercial alpha
alumina monohydrate having an average particle si~e
(APS) of 67 microns with 96 weight percent of the
particles in the 20 to 149 micron size range were
impregnated with 10 ml of solution described in
Example 1. The impregnated alumina was heated to
1000F and held at 1000F for 30 minute~. The
resultant La2O3/A12O3 sample con~ained 10
weight percent La2O3.
EXAMPLE 3
Alpha alumina monohydra~e of the type described
in Example 2 was calcined in air for one hour at
903F. 27 g of this calcined alumina was impregnated
with 10 ml of solution described in Example 1. The
impregnated sample was heated to 1000F and held at
1000F for 30 minutes. The resultant
La2O3/A12O3 sample contained 10 weight percent
lanthanum oxide La2O3.
-14-
EXAM LE 4
The procedure of Example 3 ~as repeated except
that the alumina hydrate was calcined for one hour at
1250F prior to impregnation w.ith lanthanum nitrate
solution.
EXAMPLE 5
_
The procedure of Example 3 w~s repeated, except
that the alumina hydrate was calcined for one hour at
1650F prior to impregnation with lanthanum nitrate
solution.
.
EXAMPLE 6
The procedure of Example 3 was repeated, except
that the alumina hydrate was calcined for one hour at
1850F prior to impregnation with lanthanum n:itrate
solution.
EX.~MPLE 7
The procedurle of E.xample 3 was repeated, except
that the alumina hydrate was calcined at 1950F prior
to impregnation with lanthanum nitrate solution~
EXAMPLE 8
Alumina hydrate of the type described in Example
2 was calcined in air for one hour at 1250~F. 5 ml of
the solution described in Example 1 was mixed with 5
ml of.water to yield 10 ml of solution having a
lanthanum concentration of 1~50 g of lanthanum
expressed as La2O3. 28.5 g of the calcined
-15
alumina were impregnated with the 10 ml of solution.
The impregnated sample was heated to lOOOnF and held
at 1000F for 30 minutes. The resultant
La~O3/A12O3 sample contained 5 weight percent
La23
EXAMPLE 9
Alumina hydrate of the type described in Example
2 was calcined in air for one hour at 1250F. 24 g of
this calcined alumina was impregnated with 10 ml of
solution described in Example 1. The impregnated
sample was heated to 1000F and held at 1000F for 30
minutes. After being allowed to cool to room
temperature, the impregnated and calcined sample was
given a second impregnation with 10 ml of solution
described in Example 1. After this second
impregnation, the sample was heated ta 1000F and held
at 1000F for 30 minutes. The resultant
La2O3/A12O3 sample contained 20 weight percent
La2O3.
EX~MPLE 10
A solution vf lanthanum nitrate was prepared by
dissolving 99.8g of La(NO3)3.6H2O in water to
give 100 ml of svlution. 8 ml of solution contains
3~0 g of lanthanum expressed as La2O3.
-16-
~ 3
EXAMPLE 11
Alumina hydrate was calcined in air Eor one hour
at 1250F as in Example 9. 21 g of this calcined
alumina were impregnated with 8 ml of solution
S degcribed in ~xample 10. l~he impregnated sample wa~
heated to 1000F and held at 1000F for 30 minutes.
After being allowed to cool to room temperature, the
impregnated and calcined sample was given a second
impregnation with 8 ml of solution described in
Example 10. Ater this second impregnation, the
sample was heated to 1000F and held at 1000F for 30
minutes. After being allowed to cool to room
temperature, this doubly impregnated and calcined
sample was given a third impregnation with 8 ml of
solution described in Example lOo After this third
impregnation, the sample was heated to 1000F and held
at 1000F for 30 minutes. The resultant
La2O3/A12O3 sample contained 30 weight percent
La203 -
EXAMPLE 12
The procedure of Example 11 was repeated, except
that 18.0 g of calcined alumina was used, and after
the third impregnation and calcination, the sample was
given a fourth impregnation and calcination at.
1000F. The resultant La2O3/A12O3 sample
contained 40 weight percent La~O3.
-17-
EXAMPLE 13
____
A solution of mixed rare-earth nitrates was
prepared by mixing 153.1 g of a commercial mixed
rare-earth nitrate solution with water to give 100
ml. 8 ml of the solution contained 300 g of mixed
rare-earths expressed as the oxides. The rare earth
component of this solution, expressed by weight a~
oxides, has the following composition: 60% La203,
20% Nd203, 14% C~2~ 5% Pr6ll an
10 Sm23-
EXAMPLE 14
The procedure of Example 9 was repeated, exceptthat the impregnations were carried out with 8 ml of
the solution described in Example 13. The resultant
sample contained 20 weight percent mixed rare-earth
oxides. Sixty percent of these rare-earth oxides were
lanthanum oxide, so the resultant sample contained 12
weight percent La203.
EXAMPIE 15
The procedu~e of Example 11 was r~peated, except
that the impregnations were carried out with 8 ml o
solution described in Example 13. The resultant
sample contained 30 weight percent mixed rare-earth
oxides of which 60% were lanthanum oxide. The
25 resultant sample contained 18 weight percent La203.
-18-
EXAMPLE 16
A solution of mixed rare-earth nitrates was
prepared by mixing 152.8 g of a commercial mixed
rare~ear~h nitrate solution with water ~o give 100
ml. 10 ml o~ solution contains 3.75g of mixed
rare-earth expressed as the oxides. The rare earth
component of this solution, expressed as oxidest has
the followin~ composition: 60% La203, 20
Nd203~ 14~ CeO2~ 5% Pr601] and 1~ Sm2O3.
XAMPLF 17
The procedure of Example 9 was repeated, except
that the impregnations were carried out with 10 ml of
solution described in Example 16. The resultant
sample contained 25 weight percent mixed rare-earth
oxides. Sixty percent of these rare-earth oxides
were lanthanum oxide, so the resultant sample
contained 15 weight percent La2O3.
EXAMPI,E 18
Fine-size alpha alumina monohydrate was calcined
in air for 1 hour at 1250F. This calcined alumina
had an average particle size of 15 to 20 microns.
2000 g (dry basis) of this calcined alumina was mixed
with a solution which contained 592 g of
LatN03)306H20 dissolved in 1400 ml of water in a
mechanical mixer. The solution was added at a ra~e of
100 ml per minute to this alumina. The impregnated
alumina was removed from the mixer, heated ~o 1000F
and held at 1000F for 30 minutes. The sample
contained 10 weight percent La2O3 and had an
average particle size of less than 10 microns.
. -19-
~ D
EXAMPLE 19
Alpha alumina monohydrate was calcined in air for
1 hour at 1250F ~o obtain a product having an average
particle size of 15 to 20 microns in diameter. 2000
(dry basis) of this calcined alumina was mixed with a
solution of 670 ~ of La(NO3)3.6H2O dissolved in
1400 ml of water in a mixer. The solution was added
at a rate of 100 ml per minute~ The impregnated
alumina was removed from the mixer~ heated to 100~F
10 and held at 1000F for 30 minutes. This impregnated
and calcined alumina was returned to the mixer and
given a second impregnation with 670 9 of
La(NO3)3.6H2O in 1200 ml of water which was
added at a rate of 100 ml per minute. The impregnated
15 material was heated to 1000F and held at 1000F for
30 minutes. The finished material contained ~0 weight
percent La2O3 and had an averaga particle size of
less than 10 microns.
EXAMPL 20
The finished Sx agent of Example 18 was
incorporated within the particle of an alumina-bound
cracking catalyst. The catalyst was prepared by
mixing together the following materials: The Sx
gettering agent of Example 18, a rare earth
ion-exchanged Y-type crystalline-aluminosilicate,
clay, aluminum chlorhydroxide sol (approximate
formula: A12Cl(OH)5) and water. The mixture was
spray-dried and then clacined for 2 hours at 1000F.
The proportion of starting materials were such that
the finished cataly~t contained 20 percent of the
Sx gettering agent of Example 18, 12 percent of
rare earth ion-exchanged Y-type crystalline
-20-
3~ ~
aluminosilicate, 54 percent clay and 14 percent
alumina. The finished catalyst had an average
particle size (APS) of 116 microns with 65 weight
percent o the particles in the 20 to 149 micron size
range.
EXAMPLE 21
The procedure of Example 20 was repeated except
that the Sx gettering agent of Example 19 was used.
In this Example, the finished catalyst had an
average particle size tAPS) of 77 microns with 87
weight percent o the particles in the 20 to 149
micron size range.
EXAMPLE 2:2
An alumina sol-bound cracking catalyst was
prepared by mixing together the following materials:
A ~are earth ion-exchanged Y-type crystalline
aluminosilicate (CREY~, clay, aluminum chlorhydroxide
sol (approximate formula: A12Cl(OH)5) and water.
The mixture was spray-dried and then calcined for 2
hours at 1000F. The proportion of starting materials
were such that the finished catalyst contained 12
percent of a rare earth ion-exchanged Y-type
crystalline aluminosilicate, 78 percent clay and 10
percent alumina.
The finished catalyst had an average particle size
(~PS) of 71 microns with 97 weight percent of the
particles in the 20 to 149 micron size range.
-21-
r ~
~ 9.89 9 (dry bas.is) of this alumina-bound crack~n~
catalyst was thoroughly mi~ed with 0.1110 9 (dry
basis) of an oxidation catalyst which comprises 810
ppm~platinum on a gamma alumina support having a
particle size in the fluidizable range~
EX~4PLE 23
26.89 g ~dry basis) of the cracking catalyst
described in Example 22 was thoroughly mixed with
0.1110 g ~dry basis) of the oxidation catalyst, also
described in Example 22. 3 00 g (dry basis) of a
commercial alpha alumina monohydrate was added to this
mixture and thoroughly mixed.
EX~MPLE 24
26.89 g (dry basis) of the cracking catalyst
de~cribed in Examp~e 22 was thoroughly mixed with
G.lllO ~ (dry basis~ of the oxidation catalyst, also
described in Exalmple 22. 3.00 g ~dry basis~ of the
La2O3/A12O3 comp~ition prepared in Example 2
was added to thi~ mixture and thoroughly mixed.
EXAMPLES 25-36
The procedure of Example 24 was repeated except
that the third CompOnQnt to be mixed was the
composition prepared in Example 3. Like-wise, the
procedure was repeated, except that the third
components were, in turn, the compositions prepared in
Examples 4, 5, 6, 71 B, 9, ll, 12, 14, 15, 17.
.
-22-
.;;D
EXAUPLE 3 7
29.89 9 (dry basis) of the finished caatalyst of
Example 20 was thoroughly mi~ed with 0.1110 ~ (drY
basis~ of the oxidation catalyst described in Example
22.
EXAUPLE 3B
29.89 9 (dry basis) of the inished catalyst of
Example 21 was thoroughly mixed with 0.1110 g ~dry
basis) of the oxidation catalyst de~cribed in Example
22.
EXAMPLE 39
A laboratory scale catalytic cracking unit was
used to test the catalyst compositions for their
ability to reduct Sx tSO2 ~ SO3) emissions from
the regenerator.
Prior to testing in the lab unit, the catalysts or
catalyst mixtures were steam deactivated with 100
percent steam at 15 psiq at 135nF for 8 hours. This
steam deactivation simulates the deactivation which
occurs in a commercial cat-cracking unit. The ability
of a catalyst or catalyst mixture to reduce Sx
emissions in the lab test unit after this steam
deactivation will he a measure of its ahility to
reduce Sx emissions in commercial units. In
contrast, the ability of a fresh or undeactivated
catalyst or catalyst mixture to reduce Sx emissions
in a lab test is inconclusive as far as projecting the
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~ ~3~3~
ability of the catalyst or catalyst mixture to reduce
Sx emissions in commercial ~nits, because the
catalyst or catalyst mixture would be deactivated in
the commercial unit soon after being charged to the
commercial unit and may become ineffective in reducing
Sx emissions.
In the lab unit, a low sulfur gas oil was cracked
over the catalyst or catalyst mixture at a temperature
of 980F. Regeneration of the catalyst or catalyst
mixture, i.e. t the coke-burning step, was carried out
with air at 1250F. The air used for the coke-burning
step contained 2000 ppm SO2. This is e~uivalent to
the amount of SO2 which would be formed in the
regenerator if a high sulur gas oil had been used or
the cracking step~
The regenerated catalyst or catalyst mixture was
then subjected to the cracking and steam-stripping
steps to release, as ~2S, the Sx captured in the
regenerator.
The regeneration and the cracking and
steam-stripping steps were repeated. During this
se~ond cycle, a portion of the catalyst or catalyst
mixture was removed after the regeneration step, and
another portion of the catalyst or catalyst mixture
was removed after the cracking and steam-stripping
steps.
-24-
An Sx Index which gives a measure of the Sx
captured in the regenerator and released in the
reactor and stripper was defined as
Sx Index = ~ t. ~ sulfur \ /wt.~ sul~ur
I content of the\ content of the
cataIyst or ¦ catalyst or
catalyst 1~ catalyst mixture ~ 1000
mixture after ¦ after the cracking¦
the re- ¦ and steam- ¦
~ \generation J ~tripping steps j
A sample calculation for the catalyst mixture
described in Example 31 and listed in Table I is given
below.
Sx Index - [(0.167~-(0.097)]1000 = 70
It should be noted that the Sx Index is a
measure of the amount of Sx captured in the
regenerator and released in the reactor and stripper.
A catalyst or catalyst mixture which captu~es Sx in
the regenerator, but does not release it in the
reactor and stripper would have an Sx Index of
zero. Such a catalyst or catalyst mixture would soon
become saturated, likely after one or two cycles, and
lose its effectiveness for reduction of Sx
emissions.
For long-term effectiveness, a cataly5t or
catalyst mixture must not only capture Sx in the
regenerator but be able to release it in the reactor
-25-
and stripper, and thereby restore its ability to
repeat the process.
The greater the Davison Sx Index, the greater
the-long-term effectiveness of the catalyst or
catalyst mixture in reducing Sx emi~sions from the
re~enerator. ~s s~ated above, a ~avison Sx Index
of zero means that the catalyst is not effective,
long-term, for the reduction of Sx emissions rom
the regenerator. At the other extreme, a Davison
10 Sx Iodex of 100 means essentially 100 percent
effectiveness, long-term, in the reduction of 50X
emissions from the regenerator~
The catalyst mixtures described in Examples 22,
23, 26, 31, 32, 33, 34 and 35 were tested for their
ability to reduce Sx emissions according to the
procedura described above. The Sx Indices are
given in Table I. A graphical representation of the
data in Table I (except for the catalyst mixture
described in Example 22) is set forth in the Figure
wherein Sx index is plotted against percent
La~O3 content of the Sx gettering agent in the
mixture. The curve plotted in the Figure indicates
the maximum Sx index ls obtained when the Sx
gettering agent contains about 20 percent La2O3.
~ore broadly, the data in Table I shows that the
maximum in the Sx index is obtained at La~O3
concentrations on A12O3 greater than 12 percent
and less than 30 percent (Examples 32 and 34).
~26-
Table I
L ~ ~ SOx Index
22 l0
23 1.8
26 42
34 58
31 69
32 56
33 ~4
EXAMPLE 40
- The catalyst mixtures described in Examples 37 and
. 38 were tested for their ability to reduce Sx
emissions according to the procedure described in
Example 39. The Sx Indices obtained are given in
Table II.
Table II
ehl~9~,
~O Described in Exa~ SOx~ Index
37 46
3~ 5
EXAMPLE 41
The catalyst mixtures in Examples 24, 25, 26~ ~7,
28 and 29 were tested for their ability to re~uce
- Sx emissions according to the procedure describe~
in Example 39. The Davison Sx indices obtained are
given in Table III.
-~7-
The data in Table III show the effect of
calcination of the alumina hydrate prior to
impregnat.ion with a solution of La(NO3)3.6H2O.
In-Example 24, the alumina hydrate was not calcined
prior to impregnation. In Examples 25, 26, 27, 28 and
29 the alumina hydrate was calcined at temperatures
ranging from 900F to 1950F.
TABLE III
Effect of Calcination of Alumina Prior to Impregnation
10 ~, ~
Desc~ibed in Ex~ SOx Index
24 32
26 42
27 35
28 29
29 36
; -2~-
EXAMPLE 42
The cracking catalyst u~ed in this example is a
commercially available cracking catalyst containing 17
weight percent of a rare earth ion-exchanged ~-type
crystalline aluminosilicate (REY), 63 weight percent
clay and 20 weight percent silica-alumina sol. binder.
29089 g ~dry basis) of this cracking catalyst was
through.ly mixed with 0.1110 g (dry basis) o.~ an
oxidation catalyst which comprises 810 ppm platinum
10 impregnated on a gamma alumina support having a
particle size in the fluidlzable range.
EXAMPLE 43
26.8~ g tdry basis) of the cracking catalyst
described in Example ~2 was thoro~ghly mixed with
15 0.1110 g (dry basis) of the oxidation catal.yst, also
described in Example 42. 3 . 00 g (dry basis) of a
commercial alpha alumina monohydrate was added to this
mixture and thoroughly mixed.
EXAMPLE 44
26.89 g (dry.basis) of the crackiny catalyst
described in Example 42 was thoroughly mixed with
0.1110 g (dry basis) of the oxidation catalyst, also
described in Example 42. 3.00 g (d~y basis) of the
La203/Al203 composition prepared in Example 9
was added to this mixture and thoroughly mixed.
-29-
.3
EXA~PLE 45
The catalyst mixtures described in Examples ~2~ 43
and 44 were tested for their ahility to reduce SO~
e~i-ssions according to the procedure described in
Example 39. The Sx Indices obtained are given ln
Table IV.
The results show that the silica-alumirla so.l.
cracking catalyst gave an SO~ Index o~ zero (Examp:l ~5
42~. Use of alumina as an Sx getteri.ng a~ent gave
an Sx Index of S IExample 43)~ Use of a
La2O3JA12O3 Sx ~ettering agent of this
invention gave an Sx Index of 50 ~Example 44),
which represents a considerable improvement over the
use of alumina.
TABLE IV
. . ~ .
CatalYst Mixture
Described in Exam~l~ SOx Index
. _ _
42 0
43 5
~4 50
EXAMPLE 46
. . . _
27.Q0 g (dry basis) of the cracking catalyst
described in Example 22 was thorou~hly mixed with 3~00
g (dry basis) of the La2O3/A12O3 compo.sition
prepared in Example 9. This catalyst mixtllre was
tested for its ability to reduce Sx emissi~ns
according to the procedure described in E~ample "~,
The Sx index obtained had a value of 48. This
compares with an Sx index of 6~ obtained ~or the
-30-
catalyst mixture described in Example 31 which
contains an oxidation catalyst. This shows that the
Sx gettering agent of this invention works without
the presence of an oxidation catalyst. It also shows
that the presence of an oxidation catalyst increases
the ability of the gettering agent to reduce SO~
emissions.
\
