Note: Descriptions are shown in the official language in which they were submitted.
CA 02293120 2000-03-15
1
Gasoline Sulfur Reduction in Fluid Catalytic Cracking
This invention relates to the reduction of sulfur in gasolines and other
petroleum
products produced by the catalytic cracking process. The invention provides a
s catalytic composition for reducing product sulfur and a process for reducing
the
product sulfur using this composition.
- Catalytic cracking is a petroleum refining process which is applied
commercially on a
very large scale, especially in the United States where the majority of the
refinery
to gasoline blending pool is produced by catalytic cracking, with almost all
of this coming
from the fluid catalytic cracking (FCC) process. In the catalytic cracking
process
heavy hydrocarbon fractions are converted into lighter products by reactions
taking
place at elevated temperature in the presence of a catalyst, with the majority
of the
conversion or cracking occurring in the vapor phase. The feedstock is so
converted
is into gasoline, distillate and other liquid cracking products as well as
lighter gaseous
cracking products of four or less carbon atoms per molecule. The gas partly
consists
of olefins and partly of saturated hydrocarbons.
During the cracking reactions some heavy material, known as coke, is deposited
onto
2o the catalyst. This reduces its catalytic activity and regeneration is
desired. After
removal of occluded hydrocarbons from the spent cracking catalyst,
regeneration is
accomplished by burning off the coke and then the catalyst activity is
restored. The
three characteristic steps of the catalytic cracking can be therefore be
distinguished: a
cracking step in which the hydrocarbons are converted into lighter products, a
2s stripping step to remove hydrocarbons adsorbed on the catalyst and a
regeneration
step to burn off coke from the catalyst. The regenerated catalyst is then
reused in the
cracking step.
Catalytic cracking feedstocks normally contain sulfur in the form of organic
sulfur
3o compounds such as mercaptans, sulfides and thiophenes. The products of the
cracking process correspondingly tend to contain sulfur impurities even though
about
half of the sulfur is converted to hydrogen sulfide during the cracking
process, mainly
by catalytic decomposition of non-thiophenic sulfur compounds. The
distribution of
CA 02293120 2000-03-15
2
sulfur in the cracking products is dependent on a number of factors including
feed,
catalyst type, additives present, conversion and other operating conditions
but, in any
event a certain proportion of the sulfur tends to enter the light or heavy
gasoline
fractions and passes over into the product pool. With increasing environmental
s regulation being applied to petroleum products, for example in the
Reformulated
Gasoline (RFG) regulations, the sulfur content of the products has generally
been
decreased in response to concerns about the emissions of sulfur oxides and
other
- sulfur compounds into the air following combustion processes. Reduction of
gasoline
sulfur is critical not only for the SOx emission but also for the sulfur
poisoning of
to automobile catalytic converters. The poisoning of catalytic converters will
cause other
emission problems such as NOx.
The environmental concerns have focussed extensively on the sulfur content of
motor
gasoline in view of its pre-eminent position as a vehicle fuel for passenger
cars in the
is United States. These concerns have, however, also extended to the higher
boiling
distillate fractions including the light cycle oil (LCO) and fuel oil
fractions (light fuel oil,
LFO, and heavy fuel oil, HFO) obtained from the catalytic cracking process.
With
these products, hydrodesulfurization has long been used to reduce the levels
of sulfur
in the product fractions and, in general this has proved effective. The higher
boiling
2o fractions are not, however, as amenable to desulfurization as the lower
boiling
fractions because of the increasingly refractory nature of the sulfur
compounds,
especially the substituted benzothiophenes with increasing boiling point. In
the LCO
hydrodesulfurization process, methyl and/or alkyl substitution of
benzothiophene and
dibenzothiophene makes desulfurization reactivity of the organic sulfurs
decline
2s substantially and they become "hard sulfur' or "refractory sulfur". An
example of LCO
sulfur GC is shown in Figure 1 with sulfur GC speciation. A review by Girgis
and
Gates, Ind. Eng. Chem., 30, 1991, 2021-2058. reported that substitution of a
methyl
group into the 4- position or into the 4- and 6- positions decreases the
desulfurization
activity by an order of magnitude. Houalla et al. reported activity debits of
1-10 orders
30 of magnitude, M. Houalla et al., Journal of Catalysis, 61, 1980, 523-527.
Lamure-
Meille et al. suggested that steric hindrance of the alkyl group causes the
low
reactivity of methyl substituted dibenzothiophenes Lamure-Meille et al.,
Applied
Catalysis A: General 131, 1995, 143-157. Given the utilization of the higher
boiling
CA 02293120 2000-03-15
3
catalytic cracking products as feeds for hydrodesulfurization processes, the
incentive
to reduce the incidence of the more refractory organic sulfur compounds in
these
cracking fractions becomes apparent.
s One approach has been to remove the sulfur from the FCC feed by
hydrotreating
before cracking is initiated. While highly effective, this approach tends to
be
expensive in terms of the capital cost of the equipment as well as
operationally since
hydrogen consumption is high. Another approach has been to remove the sulfur
from
the cracked products by hydrotreating. Again, while effective, this solution
has the
io drawback that valuable product octane may be lost when the high-octane
olefins are
saturated.
From the economic point of view, it would be desirable to achieve sulfur
removal in the
cracking process itself since this would effectively desulfurize the major
component of
is the gasoline blending pool without additional treatment. Various catalytic
materials
have been developed for the removal of sulfur during the FCC process cycle
but, so
far, most developments have centered on the removal of sulfur from the
regenerator
stack gases. An early approach developed by Chevron used alumina compounds as
additives to the inventory of cracking catalyst to adsorb sulfur oxides in the
FCC
2o regenerator; the adsorbed sulfur compounds which entered the process in the
feed
were released as hydrogen sulfide during the cracking portion of the cycle and
passed
to the product recovery section of the unit where they were removed. See
Krishna et
al, Additives Improve FCC Process, Hydrocarbon Processing, November 1991,
pages
59-66. The sulfur is removed from the stack gases from the regenerator but
product
2s sulfur levels are not greatly affected, if at all.
An alternative technology for the removal of sulfur oxides from regenerator
removal is
based on the use of magnesium-aluminum spinets as additives to the circulating
catalyst inventory in the FCCU. Under the designation DESOXT"" used for the
3o additives in this process, the technology has achieved a notable commercial
success.
Exemplary patents on this type of sulfur removal additive include U.S.
4,963,520;
4,957,892; 4,957,718; 4,790,982 and others. Again, however, product sulfur
levels
are not greatly reduced.
CA 02293120 2002-09-17
4
A catalyst additive for the reduction of sulfur levels in the liquid cracking
products is
proposed by Wormsbecher and Kim in U.S. Patents 5,376,608 and 5,525,210, using
a
cracking catalyst additive of an alumina-supported Lewis acid for the
production of
s reduced-sulfur gasoline but this system has not achieved significant
commercial
success. The need for an effective additive for reducing the sulfur content of
liquid
catalytic cracking products has therefore persisted.
In Canadian Patent Application Serial Na. 2,281,445, filed August 1999,
io we have described catalytic materials for use in the catalytic cracking
process which are capable of reducing the sulfur content of the liquid
products of the
cracking process. These sulfur reduction catalysts comprise, in addition to a
porous
molecular sieve component, a metal in an oxidation state above zero within the
interior of the pore structure of the sieve. The molecular sieve is in most
cases a
is zeolite and it may be a zeolite having characteristics consistent with the
large pore
zeolites such as zeolite beta or zeolite USY or with the intermediate pore
size zeolites
such as ZSM-5. Non-zeolitic molecular sieves such as MeAPO-5, MeAPSO-5, as
well
as the mesoporous crystalline materials such as MCM-41 may be used as the
sieve
component of the catalyst. Metals such as vanadium, zinc, iron, cobalt, and
gallium
2o were found to be effective for the reduction of sulfur in the gasoline,
with vanadium
being the preferred metal. When used as a separate particle additive catalyst,
these
materials are used in combination with the active catalytic cracking catalyst
(normally
a faujasite such as zeolite Y, especially as zeolite USY) to process
hydrocarbon
feedstocks in the fluid catalytic cracking (FCC) unit to produce low-sulfur
products.
2s Since the sieve component of the sulfur reduction catalyst may itself be an
active
cracking catalyst, for instance, zeolite USY, it is also possible to use the
sulfur
reduction catalyst in the form of an integrated cracking/sulfur reduction
catalyst
system, for example, comprising USY as the active cracking component and the
sieve
component of the sulfur reduction system together with added matrix material
such as
3o silica, clay and the metal, e.g. vanadium, which provides the sulfur
reduction
functionality.
CA 02293120 2002-09-17
Another consideration in the manufacture of FGC catalysts has been catalyst
stability,
especially hydrothermal stability since cracking catalysts are exposed during
use to
repeated cycles of reduction (in the cracking step) followed by stripping with
steam
and then by oxidative regeneration which produces large amounts of steam from
the
s combustion of the coke, a carbon-rich hydrocarbon, which is deposited on the
catalyst
particles during the cracking portion of the cycle. Early in the development
of zeolitic
cracking catalysts it was found that a low sodium content was required not
only for
optimum cracking activity but also for stability and that the rare earth
elements such
as cerium and lanthanum conferred greater hydrothermal stability. See, for
example,
io Fluid Catalytic Cracking with Zeolite Catalysts, Venuto et al., Marvel
Dekker, New
York, 1979, ISBN 0-8247-6870-1.
We have now developed catalytic materials for use in the catalytic cracking
process
which are capable of improving the reduction in the sulfur content of the
liquid
is products of the cracking process including, in particular, the gasoline and
middle
distillate cracking fractions. The present sulfur reduction catalyst are
similar to the
ones described in CA 2,281,445 in that a metal component in an oxidation
state above zero is present in the pore structure of a molecular sieve
component of the catalyst composition, with preference again being given to
2o vanadium. In the present case, however, the composition also comprises one
or more
rare earth elements, preferably cerium. We have found that the presence of the
rare
earth component enhances the stability of the catalyst, as compared to the
catalysts
which contain only vanadium or another metal component and that in certain
favorable
cases, especially with cerium as the rare earth component, the sulfur
reduction activity
2s is also increased by the presence of the rare earth elements. This is
surprising since
the rare earth rations in themselves have no sulfur reduction activity.
The present sulfur reduction catalysts may be used in the form of an additive
catalyst
in combination with the active cracking catalyst in the cracking unit, that
is, in
3o combination with the conventional major component of the circulating
cracking
catalyst inventory which is usually a matrixed, zeolite containing catalyst
based on a
faujasite zeolite, usually zeolite Y. Alternatively, they may be used in the
form of an
integrated cracking/ product sulfur reduction catalyst system.
CA 02293120 2000-03-15
6
According to the present invention, the sulfur removal catalyst composition
comprises
a porous molecular sieve that contains (i) a metal in an oxidation state above
zero
within the interior of the pore structure of the sieve and (ii) a rare earth
component.
s The molecular sieve is in most cases a zeolite and it may be a zeolite
having
characteristics consistent with the large pore zeolites such as zeolite beta
or zeolite
USY or with the intermediate pore size zeolites such as ZSM-5. Non-zeolitic
molecular
sieves such as MeAPO-5, MeAPSO-5, as well as the mesoporous crystalline
materials such as MCM-41 may be used as the sieve component of the catalyst.
to Metals such as vanadium, zinc, iron, cobalt, and gallium are effective. If
the selected
sieve material has sufficient cracking activity, it may be used as the active
catalytic
cracking catalyst component (normally a faujasite such as zeolite Y) or,
alternatively, it
may be used in addition to the active cracking component, whether or not it
has any
cracking activity of itself.
The present compositions are useful to process hydrocarbon feedstocks in fluid
catalytic cracking (FCC) units to produce low-sulfur gasoline and other liquid
products,
for example, light cycle oil that can be used as a low sulfur diesel blend
component or
as heating oil. Besides achieving a very significant reduction in the sulfur
content of
2o the cracked gasoline fraction, the present sulfur reduction catalyst
materials enable
the sulfur levels of light cycle oil and fuel oil products (light fuel oil,
heavy fuel oil) to be
reduced. The sulfur reduction in LCO occurs with the predominantly substituted-
benzothiophenes and substituted-dibenzothiophenes; the removal of these more
refractory species will improve the efficiency of sulfur reduction in
subsequent LCO
2s hydrodesulfurization process. The reduction in HFO sulfur may allow
upgrading of
coker products from the oil to premium coke.
While the mechanism by which the metal-containing zeolite catalyst
compositions
remove the sulfur components normally present in cracked hydrocarbon products
is
3o not precisely understood, it does involve the conversion of organic sulfur
compounds
in the feed to inorganic sulfur so that the process is a true catalytic
process. In this
process, it is believed that a zeolite or other molecular sieve provides shape
selectivity
CA 02293120 2003-07-14
with varying pore size, and the metal sites in zeolite provide adsorption
sites for the
sulfur species.
In one preferred embodiment there is provided a method of reducing the sulfur
content of a catalytically cracked petroleum fraction, which comprises
catalytically
cracking a petroleum feed fraction containing organosulfur compounds at
elevated
temperature in the presence of a cracking catalyst having a particle size from
20 to
200 microns and a product sulfur reduction catalyst which comprises a porous
molecular sieve having (i) 0.10 to 10 weight percent c~f a first metal
component
which is within the interior pore structure of the molecular sieve and which
comprises vanadium in an oxidation state greater than z~:ro and (ii) 1 to 10
weight
percent of at least one second metal component which is within the interior
pore
structure of the molecular sieve and which comprises at least one rare earth
metal
of the Lanthanide Series, from atomic member 52 to 71, of the Periodic Table,
to
produce liquid cracking products of reduced sulfur content, wherein the
molecular
sieve is a zeolite or non~zeolitic molecular sieve having an alpha value in
the range
of about 0.2 to about 2,000.
In another embodiment there is provided a fluid catalytic cracking process in
which
a heavy hydrocarbon feed containing organosulfur compounds is catalytically
cracked to lighter products by contact in a cyclic catalyst recirculation
cracking
process with a circulating fluidizable catalytic cracking catalyst inventory
consisting
of particles having a size ranging from 20 to 10() microns, by: (i)
catalytically
cracking the feed in a catalytic cracking zone operating at catalytic cracking
conditions by contacting feed with a source of regenerated cracking catalyst
to
produce a cracking zone effluent comprising cracked products and spent
catalyst
containing coke and strippable hydrocarbons; (ii) discharging and separating
the
effluent mixture into a cracked product rich vapor phase and a solids rich
phase
comprising spent catalyst; (iii) removing the vapor phase as a product and
fractionating the vapor to form liquid cracking products including gasoline;
(iv)
stripping the solids rich spent catalyst phase to remove occluded hydrocarbons
from the catalyst; (v) transporting stripped catalyst frorra the stripper to a
catalyst
CA 02293120 2003-07-14
7a
regenerator; (vi) regenerating stripped catalyst by contact with oxygen
containing
gas to produce regenerated catalyst; and (vii) recycling the regenerated
catalyst to
the cracking zone to contact further quantities of heavy hydrocarbon feed, in
which
the sulfur content of the liquid cracking products is reduced by carrying out
the
catalytic cracking in the presence of a product sulfur reduction catalyst
which
comprises a porous molecular sieve having (i) 0.10 to 10 weight percent of a
vanadium metal component which is within the interior pore structure of the
molecular sieve in an oxidation state greater than zero and (ii) 1 to 10
weight
percent of a second metal component which is within the interior pore
structure of
the molecular sieve and which comprises at least one rare earth metal of the
Lanthanide Series, from atomic number 52 to 71, of the Periodic Table, wherein
the molecular sieve is a zeolite or a non-zeolitic molecular sieve having an
alpha
value in the range of about 0.2 to about 2,fl00.
The drawings are graphs which show the performance of the present sulfur
reduction compositions as described below.
FCC Process
The present sulfur removal catalysts are used as a catalytic component of the
circulating inventory of catalyst in the catalytic cracking process, which
these days
is almost invariably the fluid catalytic cracking (FCC;' process. For
convenience, the
invention will be described with reference to the FCC process although the
present
additives could be used in the older moving bed type (TCC) cracking process
with
appropriate adjustments in particle size to suit the requirements of the
process.
Apart from the addition of the present additive to the catalyst inventory and
some
possible changes in the product recovery section, discussed below, the manner
of
operating the process will remain unchanged. Thugs, conventional FCC catalysts
may be used, for example, zeolite based catalysts with a faujasite cracking
component as described in the seminaY review by Venuto and Habib, Fluid
Ca#alytic
Cracking with Zeolite Catalysts, Marvel ~?ekker, New York 1979, ISBN 0-8247-
CA 02293120 2003-07-14
7b
6870-1 as well as in numerous other sources such as Sadeghbeigi, Fluid'
Catalytic
Cracking Handbook, Gulf Publ. Co. Houston, 1995, ISBN 0-88415-290-1.
Somewhat briefly, the fluid catalytic cracking process in which the heavy
hydrocarbon feed containing the organosulfur compounds will be cracked to
lighter
products takes place by contact of the feed in a cyclic catalyst recirculation
cracking
process with a circulating fluidizable catalytic cracking catalyst inventory
consisting
of particles having a size ranging from ~0 to 100 microns. The significant
steps in
the cyclic process are:
(i) the feed is catalytically cracked in a catalytic cracking zone, normally a
riser
cracking zone, operating at catalytic cracking conditions by contacting feed
with a
source of hot, regenerated cracking catalyst to produce an effluent comprising
cracked products and spent catalyst containing coke and strippable
hydrocarbons;
CA 02293120 2000-03-15
8
(ii) the effluent is discharged and separated, normally in one or more
cyclones, into a
vapor phase rich in cracked product and a solids rich phase comprising the
spent
rata I yst;
s
(iii) the vapor phase is removed as product and fractionated in the FCC main
column
and its associated side columns to form liquid cracking products including
gasoline,
(iv) the spent catalyst is stripped, usually with steam, to remove occluded
io hydrocarbons from the catalyst, after which the stripped catalyst is
oxidatively
regenerated to produce hot, regenerated catalyst which is then recycled to the
cracking zone for cracking further quantities of feed.
The feed to the FCC process will typically be a high boiling feed of mineral
oil origin,
is normally with an initial boiling point of at least 290°C (
550°F) and in most cases
above 315° C ( 600°F). Most refinery cut points for FCC feed
will be at least 345°C
650°F). The end point will vary, depending on the exact character of
the feed or on
the operating characteristics of the refinery. Feeds may be either distillate,
typically
with an end point of 550°C ( 1020°F) or higher, for example,
590°C ( 1095°F) or
20 620°C ( 1150°F) or, alternatively, resid (non-distillable)
material may be included in the
feed and may even comprise all or a major proportion of the feed. Distillable
feeds
include virgin feeds such as gas oils, e.g. heavy or light atmospheric gas
oil, heavy or
light vacuum gas oil as well as cracked feeds such as light coker gas oil,
heavy coker
gas oil. Hydrotreated feeds may be used, for example, hydrotreated gas oils,
2s especially hydrotreated heavy gas oil but since the present catalysts are
able to effect
a considerable reduction in sulfur, it may be possible to dispense with
initial
hydrotreatment where its objective is to reduce sulfur although improvements
in
crackability will still be achieved.
3o In the present process, the sulfur content of the gasoline portion of the
liquid cracking
products, is effectively brought to lower and more acceptable levels by
carrying out
the catalytic cracking in the presence of the sulfur reduction catalyst.
CA 02293120 2000-03-15
9
FCC Cracking Catalyst
The present sulfur reduction catalyst compositions may be used in the form of
a
separate particle additive which is added to the main cracking catalyst in the
FCCU or,
s alternatively, they may be used as components of the cracking catalyst to
provide an
integrated cracking/sulfur reduction catalyst system. The cracking component
of the
catalyst which is conventionally present to effect the desired cracking
reactions and
the production of lower boiling cracking products, is normally based on a
faujasite
zeolite active cracking component, which is conventionally zeolite Y in one of
its forms
io such as calcined rare-earth exchanged type Y zeolite (CREY), the
preparation of
which is disclosed in U.S. Patent No. 3,402,996, ultrastable type Y zeoiite
(USY) as
disclosed in U. S. Patent No. 3,293,192, as well as various partially
exchanged type Y
zeolites as disclosed in U.S. Patents Nos. 3,607,043 and 3,676,368. Cracking
catalysts such as these are widely available in large quantities from various
is commercial suppliers. The active cracking component is routinely combined
with a
matrix material such as silica or alumina as well as a clay in order to
provide the
desired mechanical characteristics (attrition resistance etc. ) as welt as
activity control
for the very active zeolite component or components. The particle size of the
cracking
catalyst is typically in the range of 10 to 100 microns for effective
fluidization. If used
2o as a separate particle additive, the sulfur reduction catalyst (and any
other additive) is
normally selected to have a particle size and density comparable to that of
the
cracking catalyst so as to prevent component separation during the sacking
cycle.
Sulfur Reduction System - Sieve Component
2s
According to the present invention, the sulfur removal catalyst comprises a
porous
molecular sieve which contains a metal in an oxidation state above zero within
the
interior of the pore structure of the sieve. The molecular sieve is in most
cases a
zeolite and it may be a zeolite having characteristics consistent with the
large pore
3o zeolites such as zeolite Y, preferably as zeolite USY, or zeolite beta or
with the
intermediate pore size zeolites such as ZSM-5, with the former class being
preferred.
CA 02293120 2000-03-15
The molecular sieve component of the present sulfur reduction catalysts may,
as
noted above, be a zeolite or a non-zeolitic molecular sieve. When used,
zeolites may
be selected from the large pore size zeolites or intermediate pore zeolites
(see Shape
Selective Catalysis in Industrial Applications, Chen et al, Marcel Dekker
Inc., New
s York 1989, ISBN 0247-7856-1, for a discussion of zeolite classifications by
pore size
according to the basic scheme set out by Frilette et al in J. Catalysis 67,
218-222
(1981 )). The small pore size zeolites such as zeolite A and erionite, besides
having
insufficient stability for use in the catalytic cracking process, will
generally not be
preferred because of their molecular size exclusion properties which will tend
to
to exclude the components of the cracking feed as well as many components of
the
cracked products. The pore size of the sieve does not, however, appear to be
critical
since, as shown below, both medium and large pore size zeolites have been
found to
be effective, as have the mesoporous crystalline materials such as MCM-41.
is Zeolites having properties consistent with the existence of a large pore
(12 ring)
structure which may be used to make the present sulfur reduction catalysts
include
zeolites Y in its various forms such as Y, REY, CREY, USY, of which the last
is
preferred, as well as other zeolites such as zeolite L, zeolite beta,
mordenite including
de-aluminated mordenite, and zeolite ZSM-18. Generally, the large pore size
zeolites
2o are characterized by a pore structure with a ring opening of at least 0.7
nm and the
medium or intermediate pore size zeolites will have a pore opening smaller
than 0.7
nm but larger than 0.56 nm. Suitable medium pore size zeolites which may be
used
include the pentasil zeolites such as ZSM-5, ZSM-22, ZSM-23, ZSM-35, ZSM-50,
ZSM-57, MCM-22, MCM-49, MCM-56 all of which are known materials. Zeolites may
25 be used with framework metal elements other than aluminum, for example,
boron,
gallium, iron, chromium.
The use of zeolite USY is particularly desirable since this zeolite is
typically used as
the active cracking component of the cracking catalyst and it is therefore
possible to
3o use the sulfur reduction catalyst in the form of an integrated
cracking/sulfur reduction
catalyst system. The USY zeolite used for the cracking component may also, to
advantage, be used as the sieve component for a separate particle additive
catalyst
as it will continue to contribute to the cracking activity of the overall
catalyst present in
CA 02293120 2000-03-15
11
the unit. Stability is correlated with low unit cell size with USY and, for
optimum
results, the UCS for the USY zeolite in the finished catalyst should be from
2.420 to
2.460 nm, preferably 2.420 to 2.455 with the range of 2.420 to 2.445 nm,
preferably
2.435 to 2.440 nm, being very suitable. After exposure to the repeated
steaming of
s the FCC cycles, further reductions in UCS will take place to a final value
which is
normally within the range of 2.420 to 2.430 nm.
In addition to the zeolites, other molecular sieves may be used although they
may not
be as favorable since it appears that some acidic activity (conventionally
measured by
to the alpha value) is required for optimum performance. Experimental data
indicate that
alpha values in excess of 10 (sieve without metal content) are suitable for
adequate
desulfurization activity, with alpha values in the range of 0.2 to 2,000 being
normally
suitable'. Alpha values from 0.2 to 300 represent the normal range of acidic
activity
for these materials when used as additives.
is
Exemplary non-zeolitic sieve materials which may provide suitable support
components for the metal component of the present sulfur reduction catalysts
inGude
silicates (such as the metallosilicates and titanosilicates) of varying silica-
alumina
ratios, metalloaluminates (such as germaniumaluminates), metallophosphates,
2o aluminophosphates such as the silico- and metalloaluminophosphates referred
to as
metal integrated aluminophosphates (MeAPO and ELAPO), metal integrated
silicoaluminophosphates (MeAPSO and ELAPSO), silicoaluminophosphates (SAPO),
gallogermanates and combinations of these. A discussion on the structural
relationships of SAPO's, AIPO's, MeAPO's, and MeAPSO's may be found in a
number
2s of resources including Stud. Surf. Catal. 37 13 - 27 (1987). The AIPO's
contain
aluminum and phosphorus, whilst in the SAPO's some of the phosphorus andlor
some
of both phosphorus and aluminum is replaced by silicon. In the MeAPO's various
metals are present, such as Li, B, Be, Mg, Ti, Mn, Fe, Co, An, Ga, Ge, and As,
in
addition to aluminum and phosphorus, whilst the MeAPSO's additionally contain
3o silicon. The negative charge of the MeaAIbPoSidOe lattice is compensated by
rations,
' The alpha test is a convenient method of measuring the overall acidity,
inclusive of both its
internal and external acidity, of a solid material such as a molecular sieve.
The test is described in
U.S. Pat. No. 3,354,078; in the Journal of Catalysis, Vol. 4, p. 527 (1965);
Vol. 6, p. 278 (1968); and
CA 02293120 2000-03-15
12
where Me is magnesium, manganese, cobalt, iron and/or zinc. Me,~4PS0's are
described in U.S. Pat. No. 4,793,984. SAPO-type sieve materials are described
in
U.S. Pat. No. 4,440,871; MeAPO type catalysts are described in U.S. Pat. Nos.
4,544,143 and 4,567,029; ELAPO catalysts are described in U.S. Pat. No.
4,500,651,
s and ELAPSO catalysts are described in European Patent Application 159,624.
Specific molecular sieves are described, for example, in the following
patents:
MgAPSO or MAPSO-U.S. Pat. No. 4,758,419. MnAPSO-U.S. Pat. No. 4,686,092;
CoAPSO-U.S. Pat. No. 4,744,970; FeAPSO-U.S. Pat. No. 4,683,217 and ZnAPSO
U.S. Pat. No. 4,935,216. Specific silicoaluminophosphates which may be used
inGude
to SAPO-11, SAPO-17, SAPO-34, SAPO-37; other specific sieve materials include
MeAPO-5, MeAPSO-5.
Another class of crystalline support materials which may be used is the group
of
mesoporous crystalline materials exemplified by the MCM-41 and MCM-48
materials.
is These mesoporous crystalline materials are described in U.S. Patents Nos.
5,098,684; 5,102,643; and 5,198,203. MCM-41, which is described in U.S.
5,098,684,
is characterized by a microstructure with a uniform, hexagonal arrangement of
pores
with diameters of at least 1.3 nm: after calcination it exhibits an X-ray
diffraction
pattern with at least one d-spacing greater than 1.8 nm and a hexagonal
electron
2o diffraction pattern that can be indexed with a d100 value greater than 1.8
nm which
corresponds to the d-spacing of the peak in the X-ray diffraction pattern. The
preferred
catalytic form of this material is the aluminosilicate although other
metallosilicates may
also be utilized. MCM-48 has a cubic structure and may be made by a similar
preparative procedure.
Metal Components
Two metal components are incorporated into the molecular sieve support
material to
make up the present catalytic compositions. One component is a rare earth such
as
lanthanum or a mixture of rare earth elements such as cerium and lanthanum.
The
other metal component can be regarded as the primary sulfur reduction
component
Vol. 61, p. 395 (1980). Alpha values reported in this specification are
measured at a constant
temperature of 538°C.
CA 02293120 2002-09-17
13
although the manner in which it effects sulfur reduction is not clear, as
discussed in CA 2,281,44, to which reference is made for a description of
sulfur reduction catalyst compositions containing vanadium and other metal
components effective for this purpose. For convenience this component of the
s composition will be referred to in this application as the primary sulfur
reduction
component. In order to be effective, this metal (or metals) should be present
inside
the pore structure of the sieve component. Metal-containing zeolites and other
mUlecular sieves can be prepared by (1 ) post-addition of metals to the sieve
or to a
catalyst containing the sieve(s), (2) synthesis of the sieves) containing
metal atoms in
to the framework structure, and by (8) synthesis of the sieves) with trapped,
bulky metal
ions in the zeolite pores. Following addition of the metal component, washing
to
remove unbound ionic species and drying and caicination should be performed.
These techniques are all known in themselves. Post-addition of the metal ions
is
preferred for simplicity and economy, permitting available sieve materials to
be
Is converted to use for the present additives. A wide variety of post-addition
methods of
metals can be used to produce a catalyst of our invention, for example,
aqueous
exchange of metal ions, solid-state exchange using metal halide salt{s),
impregnation
with a metal salt solution, and vapor deposition of metals. In each case,
however, it is
important to carry out the metals) addition so that the metal component enters
the
2o pore structure of the sieve component.
It has been found that when the metal of the primary sulfur reduction
component is
present as exchanged cationic species in the pores of the sieve component, the
hydrogen transfer activity of the metal component is reduced to the point that
2s hydrogen transfer reactions taking place during the Cracking process will
normally
maintained at an acceptably low level with the preferred metal components.
Thus,
coke and light gas make during cracking increase slightly but they remain
within
tolerable limits. Since the unsaturated light ends can be used in any event as
alkylation feed and in this way recycled to the gasoline pool, there is no
significant
30 loss of gasoline range hydrocarbons incurred by the use of the present
additives.
Because of the concern for excessive coke and hydrogen make during the
cracking
process, the metals for incorporation into the additives should not exhibit
CA 02293120 2000-03-15
14
hydrogenation activity to a marked degree. For this reason, the noble metals
such as
platinum and palladium which possess strong hydrogenation-dehydrogenation
functionality are not desirable. Base metals and combinations of base metals
with
strong hydrogenation functionality such as nickel, molybdenum, nickel-
tungsten,
s cobalt-molybdenum and nickel-molybdenum are not desirable for the same
reason.
The preferred base metals are the metals of Period 4, Groups 5, 8, 9, 12, 13
(IUPAC
classification, previously Groups VB, VIII, IIB, IIIA) of the Periodic Table.
Vanadium,
- zinc, iron, cobalt, and gallium are effective with vanadium being the
preferred metal
component. It is surprising that vanadium can be used in this way in an FCC
catalyst
to composition since vanadium is normally thought to have a very serious
effect on
zeolite cracking catalysts and much effort has been expended in developing
vanadium
suppressers. See, for example, Wormsbecher et al, Vanadium Poisoning of
Cracking
Catalysts: Mechanism of Poisoning and Design of Vanadium Tolerant Catalyst
System, J. Catalysis 100, 130-137 (1986). It is believed that the location of
the
Is vanadium inside the pore structure of the sieve immobilizes the vanadium
and
prevents it from becoming vanadic acid species which can combine deleteriously
with
the sieve component; in any event, the present zeolite-based sulfur reduction
catalysts containing vanadium as the metal component have undergone repeated
cycling between reductive and oxidativelsteaming conditions representative of
the
Zo FCC cycle while retaining the characteristic zeolite structure, indicating
a different
environment for the metal.
Vanadium is particularly suitable for gasoline sulfur reduction when supported
on
zeolite USY. The yield structure of the V/USY sulfur reduction catalyst is
particularly
is interesting. While other zeolites, after metals addition, demonstrate
gasoline sulfur
reduction, they tend to convert gasoline to C3 and C4 gas. Even though much of
the
converted C3 and Ca can be alkylated and re-blended back to the gasoline pool,
the
high C4 wet gas yield may be a concern since many refineries are limited by
their wet
gas compressor capacity. The metal-containing USY has similar yield structure
to
3o current FCC catalysts; this advantage would allow the VIUSY zeolite content
in a
catalyst blend to be adjusted to a target desulfurization level without
limitation from
FCC unit constraints. The vanadium on Y zeolite catalyst, with the zeolite
represented
by USY, is therefore a particularly favorable combination for gasoline sulfur
reduction
CA 02293120 2000-03-15
in FCC. The USY which has been found to give particularly good results is a
USY
with a unit cell size in the range from 2.420 to 2.460 nm, preferably in the
range 2.420
to 2.450, e.g. 2.435 to 2.450 nm (following treatment) . Combinations of base
metals
such as vanadium/zinc as the primary sulfur reduction component may also be
s favorable in terms of overall sulfur reduction.
The amount of the primary sulfur reduction metal component in the sulfur
reduction
- catalyst is normally from 0.2 to 5 weight percent, typically 0.5 to 5 weight
percent, (as
metal, relative to weight of sieve component) but amounts outside this range,
for
to example, from 0.10 to 10 weight percent may still be found to give some
sulfur
removal effect. When the sieve is matrixed, the amount of the primary sulfur
reduction
metal component expressed relative to the total weight of the catalyst
composition will,
for practical purposes of formulation, typically extend from 0.1 to 5, more
typically from
0.2 to 2 weight percent of the entire catalyst.
is
The second metal component of the sulfur reduction catalyst composition
comprises a
rare earth metal or metals which is present within the pore structure of the
molecular
sieve and is thought to be present in the form of rations exchanged onto the
exchangeable sites present on the sieve component. The rare earth (RE)
component
2o significantly improves the catalyst stability in the presence of vanadium.
For example,
higher cracking activity can be achieved with RE+V/USY catalyst compared to a
V/USY catalyst, while comparable gasoline sulfur reduction is obtained. Rare
earth
elements of the lanthanide series from atomic number from 57 to 71 such as
lanthanum, cerium, dysprosium, praseodymium, samarium, europium, gadolinium,
2s ytterbium and lutetium may be used in this way but from the point of view
of
commercial availability, lanthanum and mixtures of cerium and lanthanum will
normally be preferred. Cerium has been found to be the most effective rare
earth
component from the viewpoint of sulfur reduction as well as catalyst stability
and its
use is therefore preferred although good results may also be achieved with
other rare
3o earth elements, as shown below..
The amount of rare earth is typically from 1 to 10 wt. percent of the catalyst
composition, in most cases from 2 to 5 wt. percent. Relative to the weight of
the
CA 02293120 2000-03-15
16
sieve, the amount of the rare earth will normally be from 2 to 20 weight
percent and in
most cases from 4 to 10 weight percent of the sieve, depending on the
sieve:matrix
ratio. Cerium may be used in amounts from 0.1 to 10, normally 0.25 to 5,
weight
percent of the catalyst composition and relative to the sieve, will normally
be from 0.2
s to 20, in most cases from 0.5 to 10, weight percent.
The rare earth component can suitably be incorporated into the molecular sieve
component by exchange onto the sieve, either in the form of the unmatrixed
crystal or
of the matrixed catalyst. When the composition is being formulated with the
preferred
to USY zeolite sieve, a very effective manner of incorporation is to add the
rare earth
ions to the USY sieve (typically 2.445 - 2.465 nm unit cell size) followed by
additional
steam calcination to lower the unit cell size of the USY to a value typically
in the range
of 2.420 to 2.460 nm., after which the primary metal component may be added if
not
already present. The USY should have a low alkali metal (mainly sodium)
content for
Is stability as well as for satisfactory cracking activity; this will normally
be secured by the
ammonium exchange made during the ultrastabilization process to a desirable
low
sodium level of not more than 1 weight percent, preferably not more than 0.5
weight
percent, on the sieve.
2o The metal components are incorporated into the catalyst composition in a
way which
ensures that they enter the interior pore structure of the sieve. The metals
may be
incorporated directly into the crystal or into the matrixed catalyst. When
using the
preferred USY zeolite as the sieve component, this can suitably be done as
described
above, by recalcining a USY cracking catalyst containing the rare earth
component to
2s ensure low unit cell size and then incorporating the metal, e.g. vanadium,
by ion
exchange or by impregnation under conditions which permit ration exchange to
take
place so that the metal ion is immobilized in the pore structure of the
zeolite.
Alternatively, the primary sulfur reduction component and the rare earth metal
component can be incorporated into the sieve component, e.g. USY zeolite or
ZSM-5
3o crystal, after any necessary calcination to remove organics from the
synthesis after
which the metal-containing component can be formulated into the finished
catalyst
composition by the addition of the cracking and matrix components and the
formulation spray dried to form the final catalyst.
CA 02293120 2000-03-15
17
When the catalyst is being formulated as an integrated catalyst system, it is
preferred
to use the active cracking component of the catalyst as the sieve component of
the
sulfur reduction system, preferably in the form of a faujasite for example,
zeolite USY,
s both for simplicity of manufacture but also for retention of controlled
cracking
properties. It is, however, possible to incorporate another active cracking
sieve
material such as zeolite ZSM-5 into an integrated catalyst system and such
systems
- may be useful when the properties of the second active sieve material are
desired, for
instance, the properties of ZSM-5. The impregnation/exchange process should in
to both cases be carried out with a controlled amount of metal so that the
requisite
number of sites are left on the sieve to catalyze the cracking reactions which
may be
desired from the active cracking component or any secondary cracking
components
which are present, e.g. ZSM-5.
is Use of Sulfur Reduction Catalyst Composition
Normally the most convenient manner to use the sulfur reduction catalyst will
be as a
separate particle additive to the catalyst inventory. In its preferred form,
with zeolite
USY as the sieve component, the addition of the catalyst additive to the total
catalyst
2o inventory of the unit will not result in significant reduction in overall
aacking because
of the cracking activity of the USY zeolite. The same is true when another
active
cracking material is used as the sieve component. When used in this way, the
composition may be used in the form of the pure sieve crystal, pelleted
(without matrix
but with added metal components) to the correct size for FCC use. Normally,
2s however, the metal-containing sieve will be matrixed in order to achieve
adequate
particle attrition resistance and to maintain satisfactory fluidization.
Conventional
cracking catalyst matrix materials such as alumina or silica-alumina, usually
with
added clay, will be suitable for this purpose. The amount of matrix relative
to the
sieve will normally be from 20:80 to 80:20 by weight. Conventional matrixing
so techniques may be used.
Use as a separate particle catalyst additive permits the ratio of sulfur
reduction and
cracking catalyst components to be optimized according to the amount of sulfur
in the
CA 02293120 2000-03-15
18
feed and the desired degree of desulfurization; when used in this manner, it
is typically
used in an amount from 1 to 50 weight percent of the entire catalyst inventory
in the
FCCU; in most cases the amount will be from 5 to 25 weight percent, e.g. 5 to
15
weight percent. About 10 percent represents a norm for most practical
purposes. The
s additive may be added in the conventional manner, with make-up catalyst to
the
regenerator or by any other convenient method. The additive remains active for
sulfur
removal for extended periods of time although very high sulfur feeds may
result in loss
- of sulfur removal activity in shorter times.
to The alternative to the use of the separate particle additive is to use the
sulfur
reduction catalyst incorporated into the cracking catalyst to form an
integrated FCC
crackinglgasoline sulfur reduction catalyst. If the sulfur reduction metal
components
are used in combination with a sieve other than the active cracking component,
for
example, on ZSM-5 or zeolite beta when the main active cracking component is
USY,
is the amount of the sulfur reduction component (sieve plus metals) will
typically be up to
25 weight percent of the entire catalyst or less, corresponding to the amounts
in which
it may be used as a separate particle additive, as described above.
Other catalytically active components may be present in the circulating
inventory of
20 catalytic material in addition to the cracking catalyst and the sulfur
removal additive.
Examples of such other materials include the octane enhancing catalysts based
on
zeolite ZSM-5, CO combustion promoters based on a supported noble metal such
as
platinum, stack gas desulfurization additives such as DESOXT"' (magnesium
aluminum spinet), vanadium traps and bottom cracking additives, such as those
2s described in Krishna, Sadeghbeigi, op cit and Scherzer, Octane Enhancing
Zeolit'ic
FCC Catalysts, Marcel Dekker, New York, 1990, ISBN 0-8247-8399-9. These other
components may be used in their conventional amounts.
The effect of the present additives is to reduce the sulfur content of the
liquid cracking
so products, especially the light and heavy gasoline fractions although
reductions are
also achieved in the higher boiling distillate products including the light
cycle oil and
light and heavy fuel oil fractions, making this more amenable to
hydrodesulfurization
techniques by removal of the more refractory sulfur compounds. The distillate
CA 02293120 2000-03-15
19
fractions may then be hydrodesulfurized under less severe, more economical
conditions to produce distillate products suitable for use as a diesel or home
heating
oil blend component.
s The cracking process itself will be carried out in the normal manner with
the addition
of the sulfur reduction catalyst, either in the form of an additive or as an
integrated
catalytic cracking/sulfur reduction catalyst (single particle catalyst).
Cracking
- conditions will be conventional in nature.
to The sulfur removed during the cracking process by the use of the catalyst
is converted
to inorganic form and released as hydrogen sulfide which can be recovered in
the
normal way in the product recovery section of the FCCU in the same way as the
hydrogen sulfide conventionally released in the cracking process. The
increased load
of hydrogen sulfide may impose additional sour gas/water treatment
requirements but
is with the significant reductions in gasoline sulfur achieved, these are not
likely to be
considered limiting.
Very significant reductions in cracked product sulfur can be achieved by the
use of the
present catalysts, in some cases up to 50°~ relative to the base case
using a
2o conventional cracking catalyst, at constant conversion, using the preferred
form of the
catalyst described above. Gasoline sulfur reduction of 25 % is readily
achievable with
many of the additives according to the invention, as shown by the Examples
below.
For the middle distillate fractions including the LCO fraction, reductions of
up to 25
percent may also be achieved, as shown below in the Examples, coupled with a
2s reduction in the level of refractory sulfur compounds including the alkyl
substituted
benzothiophenes and dibenzothiophenes. The extent of sulfur reduction may
depend
on the original organic sulfur content of the cracking feed, with the greatest
reductions
achieved with the higher sulfur feeds. The metals content of the equilibrium
catalyst in
the unit may also affect the degree of desulfurization achieved, with a low
metals
so content, especially vanadium content, on the equilibrium catalyst favoring
greater
desulfurization. Desulfurization will be very effective with E-catalyst
vanadium
contents below 1,000 ppm although the present catalysts remain effective even
at
much higher vanadium contents. Sulfur reduction may be effective not only to
CA 02293120 2000-03-15
improve product quality but also to increase product yield in cases where the
refinery
cracked gasoline end point has been limited by the sulfur content of the heavy
gasoline fraction; by providing an effective and economical way to reduce the
sulfur
content of the heavy gasoline fraction, the gasoline end point may be extended
s without the need to resort to expensive hydrotreating, with a consequent
favorable
effect on refinery economics. Removal of the various thiophene derivatives
which are
refractory to removal by hydrotreating under less severe conditions is also
desirable if
subsequent hydrotreatment is contemplated.
to Example 1
Preparation of Catalyst Series 1
All samples in Catalyst Series 1 were prepared from a single source of spray
dried
material, consisting of 50% USY, 21 % silica sol and 29°r6 clay. The
USY had a
is starting unit cell size of 2.454 nm, Si021A1203 mol ratio of 5.46 and a
total surface area
of 810 m2g'.
A V/USY catalyst, Catalyst A, was prepared by slurrying the above spray dried
catalyst with NH40H at a pH of 6, followed by filtration, ammonium sulfate
exchange
2o and washing with water. The catalyst was calcined in the presence of steam
at
1300°F for 2 hours and impregnated with vanadyl oxalate. The steam
calcination
lowered the unit cell size of the zeolite and improved its stability in the
presence of
vanadium.
2s A V/USY catalyst, Catalyst B, was prepared in the same way as Catalyst A,
with the
exception that the initial slurrying of the catalyst was performed at a pH
between 3.2
and 3.5.
Two RE+V/USY catalysts, Catalyst C and D were prepared in the same way as
3o Catalyst B, with the exception that after ammonium sulfate exchange the
catalysts
were exchanged with solutions of rare earth chloride to add 2 and 4
wt°~ REZOs onto
the catalyst, respectively. The rare earth solution that was used had some of
its Ce3'
extracted out, thus contains only a little Ce ions.
CA 02293120 2000-03-15
21
A Ce+V/USY catalyst, Catalyst E was prepared in the same way as Catalyst B,
with
the exception that after ammonium sulfate exchange the catalyst was exchanged
with
a solution of cerium chloride to add 5% cerium (as Ce02) onto the catalyst.
These catalysts were then steamed deactivated, to simulate catalyst
deactivation in
an FCC unit, in a fluidized bed steamer at 770°C (1420°F) for 20
hours using 50°~
steam. The physical properties of the calcined and steam deactivated catalysts
are
summarized in Table 1.
to
Table 1
Physical Properties of the V, RE+V, and Ce+V USYI Silica Sol Catalysts (Series
1 )
VIUSY VI USY RE+V/ RE+V/ Ce+V/
Cat. Cat. USY USY USY
A B
Cat. C Cat. D Cat. E
Calcined Cat.
V loading, wt% 0.36 0.37 0.39 0.38 0.39
RE203 loading, N.A. N.A. 2.0 4.1 5.1
wtr6
Ce203, wtr6 N.A. N.A. 0.49 0.95 4.95
La20s. wt~ N.A. N.A. 0.96 1.83 0.03
Na20, wt~ 0.30 0.24 0.42 0.21 0.19
Unit cell size, 2.433 2.433 2.442 2.443 2.442
nm
Deactivated Cat.
(CPS 770C 20 hrs)
Surface area, 255 252 249 248 284
m2g'
Unit cell size, 2.425 2.424 2.4.26 2.428 2.428
nm
is Example 2
Preparation of Catalyst Series 2
CA 02293120 2000-03-15
22
A VIUSY catalyst, Catalyst F, was prepared using a USY zeolite with a silica-
to-
alumina ratio of 5.4 and unit cell size of 2.435 nm. A fluid catalyst was
prepared by
spray drying an aqueous slurry containing 50 wt% of the USY crystals in a
silica
sollclay matrix. The matrix contained 22-wt°r6 silica sol and 28-
wt°r6 kaolin Gay. The
s spray-dried catalyst was exchanged with NH4' by an exchange with a solution
of
ammonium sulfate and then dried. Then the USY catalyst was impregnated with a
solution of vanadium oxalate to target 0.5 wt°r6 V.
A RE+V/USY catalyst, Catalyst G, was prepared using a USY zeolite with a
silica-to-
io alumina ratio of 5.5 and a unit cell size of 2.454 nm. The USY was
exchanged with
NH4' by an exchange with a solution of ammonium sulfate. The NH4' exchanged
USY was then exchanged with rare earth rations (e.g., La3' , Ce3' , etc.) by
exchange
with a solution of mixed rare earth chlorides. The rare earth solution that
was used
had most of its Ce3' extracted out, thus contained very little Ce. The RE-
exchanged
is USY was further washed, dried, and calcined in the presence of steam in a
rotary
calciner at 760°C (1400°F). The steam calcination lowered the
unit cell size of the
zeolite to 24.40 ~ and improved its stability in the presence of vanadium. A
fluid
catalyst was prepared by spray drying an aqueous slung containing 50
wt°~ of the RE-
USY crystals in a silica sol/clay matrix. The matrix contained 22-wt°~
silica sol and
20 28-wt% kaolin clay. The spray-dried catalyst was exchanged with NH4' by .an
exchange with a solution of ammonium sulfate and was then dried and calcined
at
540°C (1000°F) for 2 hours. Following calcination, the RE/USY
catalyst was
impregnated with a VOS04 solution.
2s Catalyst H, was prepared using similar procedures as for Catalyst G except
a solution
of mixed REC13 containing mostly CeCl3 was used to exchange the USY. Catalyst
H
was prepared using a commercial USY zeolite with a silica-to-alumina ratio of
5.5 and
a unit cell size of 2.454 nm. The USY was exchanged with NH4' by an exchange
with
a solution of ammonium sulfate. The NH4'-exchanged USY was then exchanged with
3o a solution of CeCl3 containing some lanthanum. The exchanged USY was
further
washed, dried, and calcined in the presence of steam in a rotary calciner at
760°C
(1400°F). The steam calcination lowered the unit cell size of the
zeolite to 2.440 nm. A
fluid catalyst was prepared by spray drying an aqueous slurry containing 50
wt°~ of
CA 02293120 2000-03-15
23
the rare earth containing USY crystals in a silica sol/clay matrix. The matrix
contained
22-wt°r6 silica sol and 28-wt% kaolin clay. The spray-dried catalyst
was exchanged
with NH4~ by an exchange with a solution of ammonium sulfate and was then
dried
and calcined at 540°C (1000°F) for 2 hours. Following
calcination, the catalyst was
s impregnated with a VOSOa solution. Physical properties of the calcined
catalysts are
summarized in Table 2.
- Table 2
Physical Properties of V/USY, RE+VIUSY Silica-Sol Catalysts (Series 2)
to
V/USY RE+V/ USY RE+V/ USY
Catalyst Catalyst Catalyst
F G H
Calcined Cat.
V loading, wt% 0.5 0.43 0.44
RE203 loading, wt% N.A. 1.93 2.66
Ce02 loading, wt% N.A. 0.21 2.42
Na20, wt~ 0.13 0.16 0.20
Surface area, m2g-' 327 345 345
Unit cell size, nm 2.435 - -
Example 3
Preparation of Catalyst Series 3
A V/USY catalyst, Catalyst I, was prepared using a commercial H-form USY
(crystal)
with a bulk silica-to-alumina ratio of 5.4 and 2.435 nm unit cell size. A
fluid catalyst
was prepared by spray drying aqueous slurry containing 40 wt% of the USY
crystals,
wt% silica, 5 wt% alumina, and 30 wt% kaolin clay. The spray-dried catalyst
was
2o calcined at 540°C (1000°F) for 3 hours. The resulting H-form
USY catalyst was
impregnated with a vanadium oxalate solution to target 0.4 wt% V by incipient
wetness impregnation. The impregnated V/USY catalyst was further air calcined
at
540°C (1000°F) for 3 hours. The final catalyst contains 0.39% V.
CA 02293120 2000-03-15
24
A Ce+VIUSY catalyst, Catalyst J, was prepared from the same, spray-dried H-
form
USY catalyst intermediate as Catalyst I. The H-form USY catalyst was
impregnated
with a solution of Ce(N03)3 to target l.5wt% Ce loading using an incipient
wetness
impregnation method. Resulting Ce/USY catalyst was air calcined at
540°C (1000°F)
s for 3 hours followed by steaming at 540°C (1000°F) for 3
hours. Then the catalyst
was impregnated with a vanadium oxalate solution to target 0.4 wt°r6 V
by incipient
wetness impregnation. The impregnated Ce+V/USY catalyst was further air
calcined
at 540°C (1000°F) for 3 hours. The final catalyst contains 1.4%
Ce and 0.43°r6 V.
io Table 3
Physical Properties of the V and Ce+V USY/ Silica-Alumina-Clay Catalysts
(Series 3)
V/USY Ce+VI USY
CatalystCatalyst
I J
Calcined Cat.
V loading, wt% 0.39 0.43
Ce loading, wt% N.A. 1.4
Surface area, 302 250
m2g-'
Alpha 130 12
UCS, nm 2.436 2.437
is Example 4
Preparation of Catalyst Series 4
All samples in Catalyst Series 4 were prepared from a single source of spray
dried
material, consisting of 50% USY, 21 % silica sol and 29% clay. The starting
USY had
2o a bulk silica-to-alumina ratio of 5.4 and 2.435 nm unit cell size. The
spray dried
catalyst was slurried with a solution of (NHa)ZSO4 and NH40H at pH of 6 to
remove
Nar, followed by washing with water and air calcination at 650°C
(1200°F) for 2 hours.
A V/USY catalyst, Catalyst K, was prepared using the above H-form USY
catalyst.
2s The H-form USY catalyst was impregnated with a vanadium oxalate solution to
target
CA 02293120 2000-03-15
0.5 wt°~ V by incipient wetness impregnation. The impregnated VIUSY
catalyst was
further air calcined at 650°C (1200°F) for 2 hours. The final
catalyst contains 0.53°~ V.
A Ce+V/USY catalyst, Catalyst L, was prepared from the above H-form USY
catalyst.
s The H-form USY catalyst was exchanged with a solution of CeCl3 to target
0.75 wt%
Ce loading. Resulting Ce/USY catalyst was air calcined and impregnated with a
vanadium oxalate solution to target 0.5 wt% V by incipient wetness
impregnation. The
impregnated Ce+V/USY catalyst was further air calcined. The final catalyst
contains
0.72% Ce and 0.52% V.
io
A Ce+V/USY catalyst, Catalyst M, was prepared from the above H-form USY
catalyst
by an exchange with a solution of CeCl3 to target 3 wt°~ Ce loading.
Resulting
Ce/USY catalyst was air calcined and impregnated with a vanadium oxalate
solution
to target 0.5 wt% V by incipient wetness impregnation. The impregnated
Ce+V/USY
is catalyst was further air calcined. The final catalyst contains 1.5°~
Ce and 0.53°~ V.
A Ce+V/USY catalyst, Catalyst N, was prepared from the above H-form USY
catalyst
by an incipient wetness impregnation with a solution of CeCl3 to target 1.5
wt°~ Ce
loading. Resulting Ce/USY catalyst was air calcined and impregnated with a
2o vanadium oxalate solution to target 0.5 wt% V by incipient wetness
impregnation. The
impregnated Ce+V/USY catalyst was further air calcined. The final catalyst
contains
1.5% Ce and 0.53% V.
These catalysts were then steam deactivated to simulate catalyst deactivation
in an
2s FCC unit, in a fluidized bed steamer at 770°C (1420°F) for 20
hours using 50°r6 steam
and 50°~ gas. The gas stream was changed from air, N2, propylene and N2
mix, and
to Nz for every ten minutes, then circled back air to simulate the coking/
regeneration
cycle of a FCC unit (cyclic steaming). Two sets of deactivated catalyst
samples were
generated: the steam deactivation cycle was ended with air-burn (ending-
oxidation)
3o for one batch of catalysts, and the other ended with propylene (ending-
reduction).
The coke content of the "ending-reduction" catalyst is less than
0.05°r6 C. The
physical properties of the calcined and steam (ending oxidation) catalysts are
summarized in Table 4
CA 02293120 2000-03-15
26
Table 4
Physical Properties of V and Ce+V USY/ Silica Sol Catalysts (Series 4)
V/USY Ce+V/ USY Ce+VI USY Ce+VI USY
Catalyst Catalyst Catalyst Catalyst
K L M N
Calcined Cat.
V loading, wt~ 0.53 0.52 0.53 0.53
Ce loading, wtr6 N.A. 0.72 1.5 1.5
Na, ppm 890 1190 1190 1260
Deactivated Cat.(CPS
770C, 20 hrs)
Surface area, 237 216 208 204
m2g ~
Unit cell size, 2.425 2.423 2.425 2.425
nm
Example 5
Preparation of Catalyst Series 5
Alt samples in Catalyst Series 5 were prepared from a single source of spray
dried
io material, consisting of 40°~ USY, 30°~ colloidal silica sol,
and 30°r6 clay. The starting
H-form USY had a bulk silica-to-alumina ratio of 5.4 and 2.435nm unit cell
size. The
spray-dried catalyst was air calcined at 540°C (1000°F) for 3
hours.
A Ce/USY catalyst, Catalyst O, was prepared using the above H-form USY
catalyst.
is The H-form USY catalyst was impregnated with a solution of Ce(N03)3 to
target
1.5wt°~ Ce loading using an incipient wetness impregnation method.
Resulting
CeIUSY catalyst was air calcined at 540°C (1000°F) followed by
steaming at 540°C
(1000°F) for 3 hours.
2o A Ce+V/USY catalyst, Catalyst P, was prepared from Catalyst O. The Ce/USY
catalyst was impregnated with a vanadium oxalate solution to target 0.5
wt°~ V by
incipient wetness impregnation. The impregnated Ce+V/USY catalyst was dried
and
CA 02293120 2000-03-15
27
air calcined at 540°C (1000°F) for 3 hours. The final catalyst
contains 1.4°~ Ce and
0.49°~ V.
A Ce+V/USY catalyst, Catalyst Q, was prepared from Catalyst O by an exchange
with
s a solution of VOS04 at pH ~3 to target 0.5 wt°~ V loading. Resulting
Ce+V/USY
catalyst was dried and air calcined at 540°C (1000°F) for 3
hours. The final catalyst
contains 0.9°r6 Ce and 0.47% V. Physical properties of calcined
catalysts are
- summarized in Table 5.
to Table 5
Physical Properties of the Ce and Ce+V USYI Silica-Clay Catalysts (Series 5)
Ce/USY Ce+VI USY Ce+V/ USY
Catalyst Catalyst Catalyst
0 P Q
Calcined Cat.
V loading, wt~ N.A. 0.49 0.47
Ce loading, wtr6 1.6 1.4 0.9
Na, ppm - - 940
Surface area, m2g-' 284 281 272
Alpha - 10 14
Unit cell size, nm 2.435 2.436 2.436
Example 6
Preparation of RE+V/USY/Silica-Sol Catalyst
2o A RE+VIUSY catalyst, Catalyst R, was prepared using a NaY zeolite with a
silica-to-
alumina ratio of 5.5 and a unit cell size of 2.465 nm. The zeolite Y was
exchanged
with NH4' by an exchange with a solution of ammonium sulfate. The NHo'-
exchanged
Y was then exchanged with rare earth rations (e.g., La3+, Ce3+, etc.) by
exchange
with a solution of mixed rare earth chlorides from which most of the Ce3'' had
been
CA 02293120 2000-03-15
28
removed by extraction, so that the solution contained very little cerium. The
RE-
exchanged Y was further washed, dried, and calcined in the presence of steam
at
705°C (1300°F) for 2 hours. The steam calcination lowered the
unit cell size of the
zeolite and improved its stability in the presence of vanadium. A fluid
catalyst was
s prepared by spray drying an aqueous slurry containing 50 wt°~ of the
RE-USY crystals
in a silica sol/clay matrix. The matrix contained 22-wt°r6 silica sol
and 28-wt°r6 kaolin
clay. The spray-dried catalyst was exchanged with NH4~ by an exchange with a
solution of ammonium sulfate and was then dried and calcined at 540°C
(1000°F) for
1 hour. Following calcination, the REIUSY catalyst was impregnated with a
vanadium
to oxalate solution. Physical properties of the calcined catalyst are
summarized in Table
6.
Table 6
Physical Properties of RE+V USY/ Silica-Sol Catalyst
RE+V/ USY
Catalyst
R
Calcined Cat.
V loading, wt% 0.43
RE203 loading, wt% 1.93
Ce02 loading, wt% 0.21
Na20, wt% 0.16
Surface area, m2/g 345
Unit cell size, A 24.58
Example 7
Preparation of Ce+V/USY/Silica-Sol Catalyst
A Ce+VIUSY catalyst, Catalyst S, was prepared using a NaUSY zeolite with a
silica-
to-alumina ratio of 5.5 and a unit cell size of 2.454 nm. The USY was
exchanged with
NH4' by an exchange with a solution of ammonium sulfate. The NH4+ exchanged
CA 02293120 2000-03-15
29
USY was then exchanged with Ce3+ rations by exchange with a solution of cerium
chloride containing a small amount of other rare earth ions (e.g., La3+, Pr,
Nd, Gd,
etc.). The Ce-exchanged USY was further washed, dried, and calcined in the
presence of steam at 705°C (1300°F) for 2 hours. The steam
calcination lowered the
s unit cell size of the USY and improved its stability in the presence of
vanadium. A
fluid catalyst was prepared by spray drying an aqueous slurry containing 50
wt°~
CeIUSY crystals in a silica sol/clay matrix. The matrix contained 22-wt%
silica sol and
28-wt% kaolin clay. The spray-dried catalyst was exchanged with NH4+ by an
exchange with a solution of ammonium sulfate and was then dried and calcined
at
io 540°C (1000°F) for 1 hour. Following calcination, the CeIUSY
catalyst was
impregnated with a vanadium sulfate solution. Physical properties of the
calcined
catalyst are summarized in Table 7.
Table 7
is Physical Properties of Ce+V/USYI Silica-Sol Catalyst
Ce+Vl USY
Catalyst
S
Calcined Cat.
V loading, wt% 0.44
RE20s loading, wt% 2.66
Ce02 loading, wt% 2.42
Na20, wt% 0.20
Surface area, m2g-' 345
Unit cell size, nm 2.446
Experimental Procedure: Cracking Performance Evaluation
The catalysts from Examples 1 through 7 were evaluated for FCC and the results
are
reported in Examples 8 though 15. The blended catalysts (a candidate plus
equilibrium catalyst) were tested for gas oil cracking activity and
selectivity with the
CA 02293120 2000-03-15
ASTM microactivity (MAT) test, modified from ASTM procedure D-3907, using a
vacuum gas oil (VGO) feed. Some of the additive catalysts were evaluated in a
circulatory riser pilot unit using a vacuum gas oil or a hydrotreated feed.
The
compositions of the three VGO feeds and one severely cat feed hydrotreated
feed
s (CFHT) used in these Examples are shown in Table 8.
Table 8
- Properties of Cracking Feeds
Charge PropertiesVGO No. VGO No. VGO No. CFHT
1 2 3
API Gravity 26.6 22.5 24.2 23.6
Aniline Point, 83 73 187 164
C
CCR, wtr6 0.23 0.25 0.6 0.09
Sulfur, wt~ 1.05 2.59 1.37 0.071
Nitrogen, ppm 600 860 900 1200
Basic nitrogen, 310 340 290 380
ppm
Ni, ppm 0.32 - 0.2 0.2
V, ppm 0.68 - 0.1 0.2
Fe, ppm 9.15 - 0 0.3
i
Cu, ppm 0.05 - 0 0
Na, ppm 2.93 - 0.6 1.2
Sim. Dist., C
IBP, 181 217 192 172
50wt%, 380 402 430 373
99.5%, 610 553 556 547
io
CA 02293120 2000-03-15
31
A range of cracking conversions was obtained by varying the catalyst-to-oil
ratios with
the reactions run at 527°C (980°F). The ranges of cut points for
the cracked product
were:
Gasoline Cs' to 220°C ( 125 -430°F)
s Light LCO 220° to 310°C (430°F - 590°F),
Heavy LCO 310° to 370°C (590° - 700°F)
Light Fuel Oil (LFO) 220° to 370°C (430° -
700°F)
Heavy Fuel Oil (HFO) 370°C' (700°F') .
to The gasoline range product from each material balance was analyzed with a
sulfur
GC (AED) to determine the gasoline sulfur concentration. To reduce
experimental
errors in the sulfur concentration associated with fluctuations in
distillation cut point of
gasoline, the sulfur species ranging from thiophene to C4-thiophenes in
syncrude
(excluding benzothiophene and higher boiling S species) were quantitated and
the
is sum was defined as "cut-gasoline S."
To determine the sulfur content of the distillate fractions boiling above the
gasoline
range (Examples 14 and 15), the syncrude was subjected to atmospheric
distillation to
separate the gasoline. The bottoms fraction was then further vacuum distilled
to
2o generate two LFO/LCO fractions (light LCO and heavy LCO) and HFO. The
sulfur
species in the LCO sample were quantitated using a GC equipped with J&W 100 m
DB-Petro column and Sievers 3558 sulfur detector. The concentration of each
LCO
sulfur species was calculated based on the percentage of the sulfur species
from the
GC and the total sulfur content measured by XPS method.
2s
Example 8
Fluid Catalytic Cracking Evaluation of Series 1 Catalysts
The catalysts from Example 1 were steam deactivated in a fluidized bed steamer
at
30 770°C (1420°F) for 20 hours using 50% steam and 50% gas as
described in Example
4 above, ending with an air-burn (ending-oxidation). Twenty-five weight
percent of the
steamed additive catalysts were blended with an equilibrium catalyst of very
low
metals level (120 ppm V and 60 ppm Ni) from an FCC unit.
CA 02293120 2000-03-15
32
The catalytic cracking performances of the catalysts were evaluated using VGO
No. 1
as cracking feed in the microactivity test. The performances of the catalysts
are
summarized in Table 9, where the product selectivity was interpolated to a
constant
s conversion, 65wt% conversion of feed to 220°C or below (430°F-
) material.
CA 02293120 2000-03-15
33
Table 9
Catalytic Cracking Performance of Series 1 Catalysts, VGO No. 1
ECat + 25% + 25% + 25r6+ 25~ + 25~
VIUSY V/USY RE+V/ RE+ RE+
USY V/USY V/USY
Base Cat A Cat Cat Cat D Cat E
B C
Case
MAT Product
Yields
Conversion, wt% 65 65 65 65 65 65
Cat/Oil 3.0 3.3 3.3 2.9 3.0 2.9
Incremental Yield
H2 yield, wtr6 0.03 +0.05 +0.05 +0.04 +0.02 +0.04
C~ + C2 Gas, 1.1 +0.1 +0.1 +0 +0.1 +0
wtr6
Total Cs Gas, 4.3 +0.1 +0.1 -0.1 +0 -0.2
wt~
C3- yield, wt% 3.7 +0.1 +0.1 +0 +0 -0.1
Total Ca Gas, 9.3 +0.1 +0.2 -0.1 +0 -0.3
wt%
C4 yield, wt~ 4.7 +0.3 +0.4 +0.4 +0.1 +0
CS+ Gasoline, 47.6 -0.6 -0.4 +0.4 +0 +0.5
wt%
LFO, wt% 29.6 +0 +0.2 +0 +0.1 +0
HFO, wt~ 5.4 +0 -0.2 +0 -0.1 +0
Coke, wtr6 2.4 +0.3 +0.0 -0.2 -0.1 -0.1
Cut Gasoline 618 377 366 369 382 352
S,
ppm
r6 Reduction Base 39.0 40.8 40.4 38.3 43.1
in Cut
Gasoline S
The cat-to-oil ratios in Table 9 show that the blends of deactivated VIUSY and
ECat
require higher cat-to-oil ratio than the 100°~ equilibrium catalyst
base case to achieve
CA 02293120 2000-03-15
34
65°~ conversion (3.3 vs. 3.0 Cat/Oil, i.e., 10% reduction in activity).
It is due to lower
cracking activity of V/USY catalysts relative to the equilibrium catalyst. In
comparison,
addition of the RE+V/USY catalysts did not increase the cat-to-oil ratio to
achieve 65°r6
conversion. These cat-to-oil results indicate that the RE+VIUSY catalysts are
more
s stable and maintain their cracking activity better than the V/USY catalysts.
Compared to the equilibrium catalyst base case, addition of V/USY and RE+V/USY
catalyst made small changes in the overall product yield structure. There were
slight
increases in hydrogen and coke yields. Also a small changes in Ca gas,
gasoline,
io light cycle oil and heavy fuel oil yields were observed. Addition of the
V/USY and
RE+V/USY catalysts changed the gasoline S concentration substantially. When 25
wt% of each of Catalyst A or B (V/USY reference catalysts) was blended with
the
equilibrium FCC catalyst, 39.0 and 40.8 % reduction in gasoline sulfur
concentration
was achieved. When 25wt°~ of RE/USY catalysts (Catalyst C and D) was
added to
is the equilibrium catalyst, the gasoline sulfur reduction activities are
comparable to the
reference catalysts (38-40%). The RE+V/ USY catalyst containing mostly cerium
as
the rare earth metal (Catalyst E) gave a 43.1 °~ reduction in gasoline
S, to reduce the
gasoline S content by 4% additionally, i.e., 10% improvement over the V/USY
and
mixed RE/USY catalysts. All catalysts have a comparable vanadium loading (0.36
-
20 0.39%).
These results show that addition of rare earth elements improves the cracking
activity
of a V/USY catalyst. Changes in the cracked product yields are minor. Among
rare
earth ions, cerium exhibits a unique property in that the Ce+V/USY catalyst
not only
2s exhibits higher cracking activity but also exhibits increased gasoline
sulfur reduction
activity at fluid catalytic cracking conditions. The rare earth RE/USY
catalyst without
major amounts of cerium has no added benefit over V/USY for gasoline S
reduction
whereas the presence of cerium further lowered the gasoline sulfur level of
the V/USY
or RE/USY (without major cerium levels) catalysts.
CA 02293120 2000-03-15
Example 9
Comparison of Cracking Activity of Series 2 Catalysts.
The V and RE/V USY catalysts from Example 2 (Series 2 Catalysts, Catalyst F,
G, H)
s were steam deactivated at 770°C (1420°F) for various lengths
of time to compare
catalyst stability. The catalysts were steamed in a fluidized bed steamer for
2.3, 5.3,
10, 20, and 30 hours using 50% steam and 50% gas (cyclic steaming ending-
reduction, as described in Example 4 above). The surface area retentions of
the
deactivated catalysts are plotted in Figure 2.
io
The steam deactivated catalysts were tested for gas oil cracking activity
using the
ASTM microactivity test (ASTM procedure D-3907) with Vacuum Gas Oil No. 2
(above
- 2.6 wt% S). At a 30-second contact time and at 545°C (980°F)
reaction temperature,
a weight percent conversion to 220°C- (430°F-) was measured at a
constant catalyst-
is to-oil ratio of 4:1. Conversions as a function of steam deactivation time
are plotted in
Figure 3.
The surface area retentions shown in Figure 2 indicate that V/USY and RE+V/USY
catalysts show comparable surface area retention upon various hydrothermal
2o deactivation conditions suggesting that all three catalysts have comparable
framework
structure stability. However, the conversion plot shown in Figure 3 clearly
indicates
that RE+V/USY have much improved cracking activity retention as severity of
hydrothermal deactivation increases. Upon the hydrothermal deactivation, the
improvement in cracking activity from the V/USY to RE+V version was 15%
zs conversion. No apparent differences were observed between the RE versions
with
varying amounts of cerium. These results are consistent with that of Example 8
where
RE+VIUSY achieved the target conversion at a lower cat-to-oil ratio than
VIUSY.
These conversion results indicate that the RE+V/USY catalysts are more stable
and
maintain their cracking activity better than the VIUSY catalysts. The addition
of rare
3o earth ions to the USY followed by steam calcination to lower the unit cell
size of the
zeolite improved catalyst stability in the presence of vanadium.
CA 02293120 2000-03-15
36
Example 10
Fluid Catalytic Cracking Evaluation of Series 3 Catalysts
The V and Ce+V USY catalysts from Example 3 (Catalysts I, J) were steam
s deactivated in a fluidized bed steamer at 770°C (1420°F) for
20 hours using 50%
steam and 50°r6 gas, as described in Example 4 above, ending with an
air-bum
(ending-oxidation). Twenty-five weight percent of steamed additive catalysts
were
blended with the low metals FCC equilibrium catalyst (120 ppm V and 60 ppm
Ni).
The blended catalysts were then evaluated by the MAT test as described above,
using
io VGO No. 1 feed.
Performances of the Series 3 catalysts using the VGO No. 1 feed are summarized
in
Table 10, where the product selectivity was interpolated to a constant
conversion,
70wt% conversion of feed to 220°C- (430°F-) material.
is
CA 02293120 2000-03-15
37
Table 10
Catalytic Cracking Performance of Series 3 Catalysts
ECat + 25~ V/USY +25r6
Base Case cat (Catalyst Ce+V/USY cat
I)
(Catalyst
J)
MAT Product Yields
Conversion, wtr6 70 70 70
Cat/Oil 3.3 3.8 3.7
incremental Yield
H2 yield, wt~ 0.03 +0.04 +0.13
C~ + C2 Gas, wt~ 1.4 +0.1 +p.1
Total C3 Gas, wtr6 5.4 +0.1 -0.1
C3= yield, wtr6 4.5 +0,1 -0.1
Total C4 Gas, wti6 10.9 +0.2 -0.2
C4= yield, wt% 5.2 +0.4 +p.2
iC4 yield, wtr6 4.8 -0.2 -0.4
Cs' Gasoline, wtr6 48.9 -0.3 -0.3
LFO, wt~ 24.6 +0.5 +0.3
HFO, wt~ 4.7 -0.2 -0.1
Coke, wt~ 2.7 +0 +0.5
Cut Gasoline S, 529 378 235
PPM
Reduction in Cut Base 29 56
Gasoline S
Table 10 compares the FCC performances of V/USY and Ce+VIUSYI Silica-Alumina-
Clay catalysts each blended with an equilibrium FCC catalyst (ECat) after
cyclic steam
deactivation (ending oxidation). Compared to the ECat base case, the addition
of
CA 02293120 2000-03-15
38
V/USY and Ce+VIUSY catalyst changes the overall product yield structure only
slightly. Yield changes in Ca- gas, gasoline, light cycle oil, and heavy fuel
oil are all
small. Moderate increases in hydrogen and coke yields were observed. While the
product yield changes were small, the V/USY and Ce+V/USY catalysts changed the
s gasoline S concentration substantially. When 25 wt°r6 of Catalyst I
(VIUSY reference
catalyst) was blended with an equilibrium FCC catalyst, 29°~ reduction
in gasoline
sulfur concentration was achieved. In comparison, Ce+VI USY catalyst (Catalyst
J)
gave 56°r6 reduction in gasoline S. Addition of Ce to the VIUSY
catalyst reduced the
gasoline S content by additional 27%, i.e., 93°~ improvement over the
V/USY
io reference catalyst. Both catalysts have comparable vanadium loadings
(0.39°~ vs.
0.43°r6 V). In light of the fact that Ce by itself doss not have any
gasoline sulfur
reduction activity (see below in Example 11 ), these results are quite
unexpected and
clearly demonstrate the benefits of cerium addition.
is Example 11
Fluid Catalytic Cracking Evaluation of Series 4 Catalysts after Cyclic
Steaming
The performances of V and Ce+V catalysts from Example 4 are summarized in this
example. The Series 4 catalysts were steam deactivated as described above in
2o Example 4 by cyclic steaming (ending-reduction), then blended with an the
low metals
(120 ppm V and 60 ppm Ni) FCC equilibrium catalyst in a 25:75 weight ratio and
tested using VGO No. 1 feed. The results are summarized in Table 11.
CA 02293120 2000-03-15
39
Table 11
Catalytic Cracking Performance of V vs. Ce+V/USYI Silica-Sol Catalysts
ECat + 25% + 25% + 25%
Base CaseV/USY Ce+VIUSY Ce+V/USY
cat
(Cat K) (Cat M) (Cat N)
MAT Product Yields
Conversion, wtr6 65 65 65 65
CatlOil 3.0 3.4 3.2 3.3
Incremental
Yield
HZ yield, wt~ 0.03 +0.02 +0.02 +0.02
C~ + C2 Gas, wt% 1.1 +0 +0 +0.1
Total C3 Gas, 4.4 -0.1 -0.1 +0
wt~
C3 yield, wt~6 3.7 +0 -0.1 +0
Total Ca Gas, 9.5 -0.1 -0.2 -0.1
wt%
C4= yield, wt% 4.8 +0.1 +0.1 +0.1
iC4 yield, wt% 4.1 -0.2 -0.3 -0.1
CS+ Gasoline, 47.4 +0.1 +0.5 +0.1
wtr6
LFO, wt~ 29.7 -0.2 +0 -0.1
HFO, wt% 5.3 +0.2 +0 +0.1
Coke, wt~ 2.3 +0.1 -0.1 +0
Cut Gasoline S, 516 489 426 426
PPM
r6 Reduction in Base 5.2 17.4 17.4
Cut
Gasoline S
s Table 11 compares FCC performances of VIUSY and Ce+V/USYI Silica-Sol
additive
catalysts after cyclic steam deactivation (ending-reduction). Compared to the
ECat
base case, addition of the VIUSY and Ce+VIUSY catalysts made very little
changes in
the overall product yield structure. The yields of hydrogen, C4- gas,
gasoline, light
CA 02293120 2000-03-15
cycle oil, heavy fuel oil and coke were changed by less than 0.2 wt% each.
Additions
of the V/USY and Ce+V/USY catalysts changed the gasoline S concentration to
different extents. When 25 wt°~ of Catalyst K (VIUSY - reference
catalyst) was
blended with the equilibrium FCC catalyst, 5.2% reduction in gasoline sulfur
s concentration was achieved. For comparison, Ce+V/ USY catalysts (Catalysts M
and
N) gave 17.4% reduction in gasoline S, respectively. Addition of Ce to the
V/USY
catalyst reduced the gasoline S content by additional 12.3%, i.e.,
237°r6 improvement
over the V/USY reference catalyst.
to Example 12
Fluid Catalytic Cracking Evaluation of Series 4 Catalysts after Cyclic
Steaming
The performances of the V and Ce+V catalysts from Example 4 after cyclic steam
deactivation are summarized in this example. The catalysts of Example 4 were
is deactivated by cyclic steaming as described above in Example 4 (ending-
oxidation)
and were then blended with the low metals (120 ppm V and 60 ppm Ni) FCC
equilibrium catalyst in 25:75 weight ratio. The evaluation results obtained
with the
VGO No. 1 feed are summarized in Table 12.
CA 02293120 2000-03-15
41
Table 12
Catalytic Cracking Performance of V vs. Ce+VIUSY/ Silica-Sot Catalyst
ECat + 25% + 25~ + 25r6
Base V/USY cat Ce+V/USY Ce+V/USY
Case (Cat K) (Cat L) (Cat M)
MAT Product Yields
Conversion, virtr670 70 70 70
Cat/Oil 2.8 3.7 3.6 3.4
Incremental
Yield
H2 yield, wt~ 0.03 +0.12 +0.13 +0.12
C, + C2 Gas, wtr6 1.5 +0.2 +0.2 +0.1
Total C3 Gas, wtr65.5 +0.1 +0 -0.1
C3 yield, wt% 4.7 +0 +0 -0.1
Total C4 Gas, wt~ 11.1 +0 +0 -0.2
C4 yield, wt% 5.8 +0.1 +0.1 +0
iC4 yield, wt% 4.6 -0.1 -0.2 -0.2
Cs+ Gasoline, wt% 49.4 -1.0 -0.9 -0.5
LFO, wtr6 25.6 -0.1 +0 +0.2
HFO, wtr6 4.4 +0.1 +0 -0.2
Coke, wt% 2.3 +0.6 +0.5 +0.5
Cut Gasoline S, 579 283 243 224
PPM
~ Reduction in Base 51.1 58.1 61.3
Cut
Gasoline S
CA 02293120 2000-03-15
42
Table 12 compares the FCC performances of V/USY and Ce+V/USY/ Silica-Sol
additive catalysts after cyclic steam deactivation (ending-oxidation).
Compared to the
ECat base case, addition of V/USY and Ce+V/USY catalyst made slight changes in
the overall product yield structure. There were moderate increases in hydrogen
and
s coke yields. Also a small changes in Ca- gas yield gasoline, light cycle oil
and heavy
fuel oil were observed. Addition of the V/USY and Ce+V/USY catalysts changed
the
gasoline S concentration substantially. When 25 wt°~ of Catalyst K
(V/USY
- reference catalyst) was blended with an equilibrium FCC catalyst, 51.1
°r6 reduction in
gasoline sulfur concentration was achieved. In comparison, the Ce+V/USY
catalysts
io (Catalysts L and M) gave 58.1 % and 61.3% reduction in gasoline S,
respectively.
Addition of Ce to the VIUSY catalyst reduced the gasoline S content by
additional 7.0
-10.2°r6, i.e., up to 20°~ improvement over the V/USY reference
catalyst.
The product yields data of the V/USY and Ce+V/USY catalysts indicate that the
yield
is changes from the ECat is due to addition of vanadium to the USY catalyst.
The
product yields of V/USY catalyst is comparable to those of Ce+V/USY catalysts
except
the gasoline S level. These results suggest that Ce increases the gasoline
sulfur
reduction activity of the V/USY additive catalyst with little effect on
product yields.
zo Example 13
Fluid Catalytic Cracking Evaluation of Series 5 Catalysts, Study of
Promotional Effects
Performances of the Ce and Ce+V catalysts from Example 5 after cyclic steaming
deactivation (ending-reduction) as described above, are summarized in this
example.
2s The deactivated catalysts were blended with the low metals (120 ppm V and
60 ppm
Ni) FCC equilibrium catalyst in 25:75 weight ratio. The results obtained with
the VGO
No. 1 feed are summarized in Table 13.
CA 02293120 2000-03-15
43
Table 13
Catalytic Cracking Performance of Ce vs. Ce+VIUSYI Silica-Clay Catalysts
ECat Base + 25~ + 25~ + 25~6
Case Ce/USY Ce+V/USY Ce+VIUSY
(Cat (Cat P) (Cat Q)
O)
MAT Product Yields
Conversion, wt% 70 70 70 70
Cat/Oil 3.2 3.4 3.7 3.9
Incremental
Yield
HZ yield, wtr6 0.04 +0 +0.07 +0.07
C~ + C2 Gas, wt% 1.5 +0.1 +0.1 +0.1
Total C3 Gas, 5.7 +0.1 -0.1 +0
wt%
C3 yield, wt% 4.8 +0 +0 +0
Total C4 Gas, 11.5 +0 -0.3 -0.1
wt~
C4 yield, wt~ 5.7 +0 +0.1 +0.1
iC4 yield, wtr6 4.9 +0 -0.3 -0.2
C5+ Gasoline, 48.8 -0.2 -0.2 -0.7
wt~
LFO, wt% 25.5 +0 +0.1 +0.1
HFO, wt% 4.5 +0 -0.1 -0.1
Coke, wt% 2.4 +0 +0.3 +0.6
Cut Gasoline S, 486 487 341 351
PPM
~ Reduction in Base 0 29.8 27.7
Cut
Gasoline S
Table 13 compares FCC performances of Ce/USY and Ce+V/USYI Silica-clay
additive
catalysts after cyclic steam deactivation (ending-reduction). Compared to the
ECat
base case, addition of the Ce/USY catalyst made almost no changes in overall
CA 02293120 2000-03-15
44
product yields. Addition of the Ce+V/USY catalyst made slight changes in the
overall
product yield structure. There were moderate increases in hydrogen and coke
yields,
as well as slight changes in C4- gas, gasoline, light cycle oil and heavy fuel
oil yields.
Addition of the Ce/USY catalysts made a no change in the gasoline S
concentration.
s In contrast, Ce+V/USY catalysts (Catalysts P and Q, invention) gave
29.8°r6 and
27.7°r6 reduction in gasoline S, respectively. These results indicate
that cerium by
itself does not have any gasoline sulfur reduction activity. Cerium appears to
have a
promotional effect for vanadium to increase the activity of a V/USY gasoline
sulfur
reduction additive catalyst.
io
Example 14
Catalyst R was evaluated in a circulating riser pilot unit (Davison
Circulating Riser) in
combination with a typical FCC equilibrium catalyst using VGO No. 3 feed
(Table 8).
is Prior to evaluation, the RE+V USY catalyst was steam deactivated at
770°C (1420°F)
for 20 hours using 50°r6 steam and 50% gas. Twenty-five weight percent
of steamed
additive catalyst was blended with an equilibrium catalyst (530 ppm vanadium
and
330 ppm Ni) from an FCC unit.
2o FCC performances of the catalysts are summarized in Table 14, where the
product
selectivity was interpolated to a constant conversion, 75wt% conversion of
feed to
220°C- (430°F-) material.
CA 02293120 2000-03-15
4s
Table 14
Catalytic Cracking Performance of RE+V/USY/ Silica-Sol Catalyst
E~ + 25% RE+VlUSY
Base Case Cat R
Riser Product Yields
Conversion, wt% 75 75
Cat/Oil 7.0 6.7
Incremental Yield
H2 yield, wt% 0.03 +0.01
Total Cs, wt~ 6.5 -0.1
Total Ca, wt% 12.1 -0.1
C5+ Gasoline, wtr6 49.4 -0.1
LFO, wt% 18.3 -0.1
HFO, wt% 6.7 +0.1
Coke, wtr6 4.1 +0.3
Cut Gasoline S, ppm 735 589
LCO Sulfur, wt% 2.36 2.16
r6 Reduction in Gasoline Base 20
Sulfur
Reduction in LCO Sulfur Base 9
s Compared to the base case, addition 25 wt% of the RE+V/USY catalyst made
small
changes in the overall product yield structure. There were negligible
increases in H2
and coke yields. Also little changes in Ca- gas, gasoline, light cycle oil and
heavy fuel
oil yields were observed. Addition of the RE+VIUSY catalyst changed the
gasoline
sulfur concentration substantially, 20 % reduction in gasoline sulfur
concentration
io being achieved. In addition to the gasoline sulfur reduction, a substantial
sulfur
reduction in LCO was observed, equivalent to an overall reduction of 9% LCO
sulfur.
The sulfur species in LCO are shown in Table 15 and Figure 4. The LCO contains
wide ranges of benzothiophene and dibenzothiophene sulfur species. The sulfur
CA 02293120 2000-03-15
46
reductions were more prominent for substituted-benzothiophenes and substituted-
dibenzothiophenes such as Cs'-benzothiophenes, and C~- through C4'-
dibenzothiophenes. The results are quite unexpected since substituted
dibenzothiophenes are bulkier and expected to be harder to crack and
desulfurize in
s FCC.
Table 15
Sulfur Speciation of LCO from VGO Feed No. 3
(wt% sulfur in LCO) ECat + 25% RE+VlUSY
Base CaseCat 1
Benzothiophene 0.04 0.04
C~-Benzothiophenes 0.22 0.24
C2-Benzothiophenes 0.39 0.38
C3+-Benzothiophenes 0.47 0.38
Dibenzothiopehene 0.10 0.09
C~-Dibenzothiophenes 0.36 0.32
C2-Dibenzothiophenes 0.39 0.35
Cs-Dibenzothiophenes 0.24 0.22
C4+-Dibenzothiophenes 0.16 0.14
Sum 2.36 2.16
to Example 15
Fluid Catalytic Cracking Evaluation of Ce+V/ USY/ Silica-Sol Catalysts
The Ce+V/USY catalyst from Example 7 (Catalyst S) was evaluated in a
circulating
is fluidized cracking unit for 40 days in combination with a typical FCC
catalyst using the
severely hydrotreated FCC feed of Table 8 (CFHT Feed). The base FCC
equilibrium
catalyst has very low metals level (200 ppm V and 130 ppm Ni). For the first
15 days,
a 50/50 blend of fresh FCC catalyst and the Ce+VIUSY catalyst from Example 7
was
added to the FCC regenerator at 1.4% of the catalyst inventory pre day. From
15~" to
Zo 40~h day, a 85/15 blend of the fresh FCC catalyst and the Ce+VIUSY catalyst
was
added to the FCC regenerator at 1.4% of the catalyst inventory per day. The
CA 02293120 2000-03-15
47
regenerator temperature was maintained at approximately 705°C
(1300°F) throughout
the evaluation. Two equilibrium catalyst (ECat) samples were collected: the
first was
sampled before the Ce+V/USY addition (base case) and the second at 40~" day.
Based on Ce and V analysis, the loading of the Ce+VIUSY catalyst is estimated
as
s 12%.
FCC performances of the catalysts are summarized in Table 16, where the
product
selectivity was interpolated to a constant conversion, 70wt°~
conversion of feed to
220°C- (430°F-) material.
io
CA 02293120 2000-03-15
48
Table 16
Catalytic Cracking Performance of Ce+V/USYI Silica-Sol Catalyst
ECat + 12% Ce+VlUSY
Base Case Cat S
Riser Product Yields
Conversion, wtr6 70 70
Cat/Oil 6.5 6.4
Incremental Yield
HZ yield, wt~6 0.02 +0.0
Total C3, wtr6 4.8 +0.0
Total C4, wtr6 9.3 +0.1
CS+ Gasoline, wt% 51.9 -0.2
LFO, wtr6 24.0 -0.2
HFO, wt% 6.1 +0.1
Coke, wtr6 2.6 +0.1
Cut Gasoline S, ppm 100 79
Light LCO Sulfur, ppm 815 599
Heavy LCO Sulfur, ppm 1957 1687
HFO Sulfur, ppm 2700 1700
r6 Reduction in Gasoline Base 21
Sulfur
r6 Reduction in light LCO Base 27
S
r6 Reduction in Heavy LCO Base 14
S
r6 Reduction in HFO SulfurBase 37
Wt% S of spent catalyst <0.06 <0.06
s Compared to the ECat base case, addition of the Ce+V/USY catalyst made small
changes in the overall product yield structure. There were negligible
increases in H2
and coke yields. Also little changes in Ca gas, gasoline, light cycle oil and
heavy fuel
CA 02293120 2000-03-15
49
oil yields were observed. Addition of the Ce+V/USY catalyst changed the
gasoline S
concentration substantially. When 12 wt% of Ce+V/USY catalyst was blended in
the
equilibrium FCC catalyst, 21 % reduction in gasoline sulfur concentration was
achieved. In addition to the gasoline sulfur reduction, substantial sulfur
reductions in
s LCO and HFO were observed.
The sulfur species in the light LCO fraction were analyzed using a sulfur GC.
The
- concentration of each organo-sulfur class was as shown in Table 17 and
Figure 5 for
light LCO.
io
Table 1 T
Sulfur Speciation of Light LCO from CFHT Feed
(PPM suliur in light ECat +12% Ce+VIUSY
LCO)
Base Case Cat J
Cs'Thiopenes 4 1
Benzothiophene 20 14
C~-Benzothiophenes 141 106
CrBenzothiophenes 237 174
C3'-Benzothiophenes 295 215
Dibenzothiopehene 17 14
C~-Dibenzothiophenes 47 34
C~-Dibenzothiophenes 32 25
C3-Dibenzothiophenes 20 13
C4'-Dibenzothiophenes 3 1
Sum 815 599
is
As shown in Figure 5, the light LCO contains mainly benzothiophene sulfur
species.
The sulfur reductions, equivalent to an overall 27 percent reduction in the
light LCO
sulfur, were more prominent for substituted benzothiophenes such as C,-
through C3'-
benzothiophenes. The results are quite unexpected since substituted
CA 02293120 2000-03-15
benzothiophenes are bulkier, and they are expected to be harder to crack and
desulfurize in FCC.
The sulfur species in the heavy LCO fraction were as shown in Table 18 and
Figure 6.
s The heavy LCO contains mainly dibenzothiophene sulfur species. The sulfur
reductions (14 percent overall for heavy LCO) were more prominent for
substituted
dibenzothiophenes such as C~- through Ca'-dibenzothiophenes. The results are
quite
- unexpected since substituted dibenzothiophenes are bulkier and expected to
be
harder to crack and desulfurize in FCC.
io
CA 02293120 2000-03-15
51
Table 18
Sulfur Speciation of Heavy LCO from CFHT Feed
(PPM sulfur in heavy ECat + 12~ Ce+V/USY
LCO)
Base Case (Cat S)
Benzothiophene 0 0
C~-Benzothiophenes 2 1
CrBenzothiophenes 12 7
C3'-Benzothiophenes 128 86
Dibenzothiopehene 65 54
C~-Dibenzothiophenes 361 312
C2-Dibenzothiophenes 537 480
C3-Dibenzothiophenes 475 425
C4;-Dibenzothiophenes 378 322
Sum 1957 1687
s
The sulfur reduction catalyst is active in reducing benzothiophene and
dibenzothiophene sulfur species as well as thiophene sulfur species. The
reduction of
sulfur takes place predominantly for substituted benzothiophenes and
substituted
dibenzothiophenes. These results suggest that C-S bonds in alkyl substituted-
to thiophenes are more reactive and susceptible to cracking.
The facile sulfur reduction of substituted-thiophenes, substituted-
benzothiophenes,
and substituted-dibenzothiophenes was quite unexpected and will enhance the
effectiveness of a subsequent LCO hydrodesulfurization process. It is well
known for
is LCO hydrodesulfurization process that methyl andlor alkyl substitution of
benzothiophene and dibenzothiophene makes desulfurization reactivity of the
organic
sulfurs decline substantially and become "hard sulfur" or "refractory sulfur".
Our LCO
containing a lower amount of substituted benzo and dibenzothiophenes will
generate
a diesel fuel with a lower sulfur content after a hydrodesulfurization process
than the
2o comparable LCO generated by a conventional FCC catalyst.
