Process for the demetallization of FCC catalyst

A process is disclosed for passivating the reactivity of contaminant metals, such as nickel and vanadium, which have been deposited on a catalytic cracking catalyst, by adding to the cracking catalyst a mixture of a calcium-containing material and a magnesium-containing material in a separate reactor in the presence of steam. The preferred calcium-containing material is dolomite and the preferred magnesium-containing material is sepiolite. It is also preferred to include antimony and/or bismuth compounds in the additive mixture.

FIELD OF THE INVENTION 
This invention relates to a process capable of removing vanadium from 
vanadium-contaminated FCC catalyst and passivating the nickel in a 
nickel-contaminated FCC catalyst in order to restore the activity and 
selectivity of the catalyst. Such FCC catalyst comprises catalytically 
active crystalline aluminosilicate zeolite. 
BACKGROUND OF THE INVENTION 
In ordinary catalytic cracking processes, various metallic contaminants 
which are present in hydrocarbonaceous feedstock, particularly vanadium, 
nickel, copper and iron, cause the degradation and/or deactivation of the 
catalytic cracking catalyst. Particularly susceptible to vanadium 
contamination are crystalline aluminosilicate zeolites, either natural or 
synthetic. This deactivation causes distillate yield loss, particularly 
through loss of active acid cracking sites, as well as metal poisoning via 
secondary dehydrogenation and coking reactions caused by the deposition of 
these heavy metals on the catalyst. Remedial technology has evolved in 
various ways to deal with this metals contaminant problem. 
For example, one method uses metallic compound additives to the catalyst or 
the hydrocarbon oil which compound additives serve to passivate the 
metallic contaminants on the catalyst. U.S. Pat. No. 4,432,890, Beck et 
al., teaches a catalyst composition comprising a crystalline 
aluminosilicate zeolite dispersed in an amorphous inert solid matrix 
containing a metal additive. The metal additive may be introduced into the 
catalyst during the cracking process or during catalyst manufacture. Metal 
additives include water soluble inorganic metal salt and hydrocarbon 
soluble inorganic metal salts, and hydrocarbon soluble organometallics of 
selected metals. U.S. Pat. No. 3,977,963, Readal et al., teaches a method 
of negating the effects of metals-poisoning on a cracking catalyst by 
contacting the metal-contaminated catalyst with a bismuth or manganese 
compound. U.S. Pat. No. 4,101,417, Mitchell et al., would add 2000 ppm of 
tin to the catalyst for the same purpose. In U.S. Pat. No. 4,784,752, 
Ramamoorthy et al., disclose the addition of a passivating agent 
containing bismuth in a weight ratio of bismuth to "nickel equivalents" 
consisting of nickel, iron and vanadium. In U.S. Pat. No. 4,083,807, 
Mitchell et al., an improved cracking catalyst is obtained by 
incorporating into a crystalline aluminosilicate catalyst by ion exchange 
a substantial concentration of a metal selected from antimony, bismuth and 
manganese. U.S. Pat. No. 4,990,240, Pasek et al., teaches zeolite 
passivation of vanadium in terms of a passivation factor greater than 2.0 
for selected Group IIA metal compounds. U.S. Pat. No. 4,929,583, Pasek et 
al., claims the catalyst composition comprising this vanadium passivator. 
U.S. Pat. No. 4,036,740, Readal et al., teaches a selected catalytic 
cracking process using a bismuth, antimony or manganese treating agent to 
maintain a selected volume ratio of carbon dioxide to carbon monoxide in 
the gaseous effluent. The disclosures of the aforementioned patents are 
incorporated herein as if fully set forth in ipsis verbis. 
Another mechanism includes the use of various diluents as metals 
passivators or traps. The traps contain materials which will chemically 
combine with and effectively tie up the offending materials. These traps 
have proved particularly effective with regard to vanadium. 
One strategy utilizing this mechanism involves the use of dual particle 
systems wherein the cracking catalyst, usually zeolitic, is contained on 
one particle or component of the system, and a diluent or vanadium trap is 
contained as a separate, distinct entity on a second particle or component 
of the system. U.S. Pat. No. 4,465,588, Occelli et al., discloses a 
process for cracking high metals content feedstock using a novel catalyst 
cracking composition comprising a solid cracking catalyst and a separate 
and distinct diluent which contains materials selected from magnesium 
compounds, or a selected magnesium compound in combination with one or 
more heat-stable metal compounds. Among the magnesium-containing compounds 
specified is magnesium clay sepiolite. U.S. Pat. No. 4,465,779 teaches the 
cracking catalyst of '558 itself. U.S. Pat. No. 4,615,996, Occelli, 
teaches a dual-function cracking catalyst composition comprising a solid 
cracking catalyst and a separate, distinct particle diluent containing 
substantially catalytically inactive crystalline aluminosilicate. U.S. 
Pat. No. 4,466,884, Occelli et al., teaches a process wherein the separate 
and distinct entity diluent contains antimony and/or tin, supported on an 
inert base selected from the group consisting of magnesium-containing clay 
minerals, including sepiolite. U.S. Pat. No. 4,650,564, Occelli et al., 
also teaches a process for cracking high metals content feedstock 
comprising contacting the feed with a dual particle catalyst cracking 
composition comprising a solid cracking catalyst and, as a separate and 
distinct entity, an alumina diluent. U.S. Pat. No. 4,944,865, Occelli et 
al., also teaches a dual particle catalytic cracking system comprising a 
cracking catalyst and a second component comprising magnesium oxide. U.S. 
Pat. No. 4,707,461, Mitchell et al., discloses a catalyst composition 
comprising zeolite, matrix, and a calcium-containing additive comprising 
substantially amorphous calcium silicate as a separate and discrete 
component. A preferred calcium additive component comprises dolomite. 
One primary issue involving the use of the dual particle systems in fluid 
catalytic cracking is that the effect of the diluent particle on yield is 
such that the activity of the active catalyst must be very high in order 
to compensate for the dilution effect. It would therefore be helpful to 
develop a dual particle catalyst wherein the diluent could be added in low 
amounts and have enhanced metals scavenging ability, in particular 
vanadium. Secondarily, it would be advantageous for the catalyst system to 
demonstrate higher sulfur tolerance than previous known systems, as some 
feeds requiring processing have high enough sulfur levels to cause process 
difficulties with known catalysts. 
Related patent U.S. Pat. No. 4,988,654, Kennedy and Jossens, claims such a 
dual component catalyst composition for the catalytic cracking of 
metal-containing hydrocarbonaceous feedstock comprising as a first 
component an active cracking catalyst; and as second component, a separate 
and distinct particle comprising a selected calcium and magnesium 
containing material; a magnesium containing material comprising a hydrous 
magnesium silicate; and a selected binder. U.S. Pat. No. 5,002,653, 
Kennedy and Jossens, claims the catalytic cracking process with the dual 
component catalyst of '654. Related patent application U.S. Ser. No. 
590,538, filed Sep. 27, 1990, claims the second component of the dual 
component catalyst system. The disclosure of U.S. Ser. No. 590,538 is 
incorporated herein by reference. The preferred second component comprises 
dolomite and sepiolite. U.S. Pat. No. 4,196,102, Inooka et al., relates to 
a hydrotreating catalyst comprising selected catalytic metals on a 
sepiolite carrier. U.S. Pat. No. 4,343,723, Rogers et al., teaches the use 
of clays with crystalline aluminosilicate zeolite in catalytic 
compositions. U.S. Pat. No. 4,439,312, Asaoko et al., provides a catalyst 
for hydrotreating heavy oil, including a carrier which is a calcined 
mixture of selected magnesium silicate and selected pseudoboehmite. U.S. 
Pat. No. 4,929,338, Wormsbecker, reports a catalytic cracking catalyst for 
vanadium-containing hydrocarbons having a selected dolomite component 
mixed with a zeolite cracking catalyst as an integral component or as a 
separate additive. The disclosure of the aforementioned patents are 
incorporated herein as if fully set forth in ipsis verbis. 
To carry this strategy one step further, it would be advantageous if, for 
example, a dolomite/sepiolite particle additive when added to an FCC 
catalyst inventory contaminated with vanadium, either in situ, in the FCC 
unit, or by treatment of the contaminated catalyst ex situ, would take up 
vanadium from the catalyst. It would also be advantageous if a metallic 
passivator, as heretofore described, were incorporated into the additive 
to render nickel contaminants inert in place on the catalyst. It would be 
especially advantageous if after such treatment with the additive, the 
catalyst would regain its activity without removal of the additive from 
the catalyst inventory. However, it would suffice if re-activated catalyst 
were separable from the additive, separated and reused. 
This strategy, if successful, would result in a rejuvenated catalyst having 
the following benefits: Revived catalyst activity offering higher FCC 
conversion or feed throughput; Removal of pore blocking vanadium; Reduced 
fresh catalyst consumption; The opportunity for accommodating heavier oil 
feedstocks, or residuum. 
SUMMARY OF THE INVENTION 
The present invention is a process for the removal of contaminant metals 
from contaminated catalytic cracking catalyst. The process is particularly 
effective for the removal of vanadium from cracking catalyst. It can also 
accommodate the passivation of active nickel on the surface of the 
catalyst. The process comprises the step of contacting the contaminated 
particulate catalyst with a selected additive material in a separate 
distinct particle. The selected additive material comprises a 
calcium-containing material in combination with a magnesium-containing 
material, wherein the calcium-containing compound is active for metals 
trapping, especially vanadium trapping. The preferred calcium-containing 
material is dolomite and the preferred magnesium-containing material is 
sepiolite. In an embodiment of the invention, the selected additive 
material contains antimony, bismuth, or an antimony, bismuth compound on 
the separate distinct particle. Upon contacting with contaminated 
particulate catalyst under fluidized catalytic cracking conditions, and in 
particular under regenerative fluidized catalytic cracking conditions 
which generally comprise oxidizing high temperature conditions, one of the 
contaminants, vanadium, is found to transfer to the additive particles, 
where it is effectively rendered inert. In a final step, the additive 
particles may be separated from the catalyst particles. The use of 
antimony or bismuth in the process offers the additional advantage of 
passivating metal contaminants such as nickel which are not transferred 
from the contaminated catalyst to the additive particles; rather the 
antimony or bismuth species can transfer to the immobilized nickel 
contaminant to negate its dehydrogenation activity.

DETAILED DESCRIPTION OF THE INVENTION 
FCC Catalyst 
The fluid catalytic cracking catalyst can be any cracking catalyst of any 
desired type having high activity. By "high activity" we mean catalyst of 
fresh MAT Activity above about 1.0, preferably up to about 4.0, or even 
higher, where 
##EQU1## 
The "MAT Activity" was obtained by the use of a microtest (MAT) unit 
similar to the standard Davison MAT (see Ciapetta et al., Oil & Gas 
Journal, 65,88 (1967), or as defined in ASTM standard test No. D 3907-87. 
Preferably, the host catalyst used herein is a catalyst containing a 
crystalline aluminosilicate, preferably exchanged with rare earth metal 
cations, sometimes referred to as "rare earth-exchanged crystalline 
aluminum silicate" or one of the stabilized hydrogen zeolites. Typical 
zeolites or molecular sieves having cracking activity which can be used 
herein as a catalytic cracking catalyst are well known in the art. 
Suitable zeolites are described, for example, in U.S. Pat. No. 3,660,274 
to Blazek et al., or in U.S. Pat. No. 3,647,718 to Hayden et al., or in 
U.S. Pat. No. 4,493,902 to Brown et al., which are incorporated herein by 
reference. Synthetically prepared zeolites are initially in the form of 
alkali metal aluminosilicates. The alkali metal ions are typically 
exchanged with rare earth metal and/or ammonium ions to impart cracking 
characteristics to the zeolites. The zeolites are crystalline, 
three-dimensional, stable structures containing a large number of uniform 
openings or cavities interconnected by smaller, relatively uniform holes 
or channels. The effective pore size of synthetic zeolites is suitably 
between 6 and 15 .ANG. in diameter. The overall formula for the preferred 
zeolites can be represented as follows: 
EQU H.sub.(2-X) .multidot.XM.sub.2/n O:A1.sub.2 O.sub.3 :1.5-6.5 SiO.sub.2 
:yH.sub.2 O 
where M is a metal cation and n its valence and x varies from 0 to 1 and y 
is a function of the degree of dehydration and varies from 0 to 9. M is 
preferably a rare earth metal cation such as lanthanum, cerium, 
praseodymium, neodymium or mixtures of these. 
Zeolites which can be employed herein include both natural and synthetic 
zeolites. These zeolites include gmelinite, chabazite, dachiardite, 
clinoptilolite, faujasite, beta, heulandite, analcite, levynite, erionite, 
sodalite, cancrinite, nepheline, lazurite, scolecite, natrolite, 
offretite, mesolite, mordenite, brewsterite, ferrierite, and the like. The 
faujasites are preferred. Suitably synthetic zeolites which can be treated 
in accordance with this invention include zeolites X, Y, including 
chemically or hydrothermally dealuminated high silica-alumina Y, A, L, 
ZK-4, beta, ZSM-types or pentasil, boralite and omega, SZ-26 and SZ-33. 
The term "zeolites" as used herein contemplates not only aluminosilicates 
but substances in which the aluminum is replaced by gallium or boron and 
substances in which the silicon is replaced by germanium. The preferred 
zeolites for this invention are the synthetic faujasites of the types Y 
and X or mixtures thereof. 
To obtain good cracking activity the zeolites have to be in a proper form. 
In most cases this involves reducing the alkali metal content of the 
zeolite to as low a level as possible. Further, a high alkali metal 
content reduces the thermal structural stability, and the effective 
lifetime of the catalyst will be impaired as a consequence thereof. 
Procedures for removing alkali metals and putting the zeolite in the 
proper form are well known in the art, for example, as described in U.S. 
Pat. No. 3,537,816. 
The crystalline aluminosilicate zeolites, such as synthetic faujasite, 
will, under normal conditions, crystallize as regularly shaped, discrete 
particles of approximately 1 to 10 microns in size, and, accordingly, this 
is the size range normally used in commercial catalysts. The particle size 
of the zeolites can be, for example, from about 0.1 to about 10 microns, 
but generally from about 1 to about 5 microns or less. Crystalline 
zeolites exhibit both an interior and an exterior surface area, with the 
largest portion of the total surface area being internal. Blockage of the 
internal channels by, for example, coke formation and contamination by 
metals poisoning will greatly reduce the total accessible surface area, 
and, thereby, the efficiency of the catalyst. The crystalline alkali metal 
aluminosilicate can, therefore, by preferably cation-exchanged by 
treatment with a solution essentially characterized by a pH in excess of 
about 4.5, preferable by a pH in excess of 5, and containing an ion 
capable of replacing the alkali metal and activating the catalyst, 
excepting in the case of rare earth cations where the pH should be less 
than 5.0 but greater than 4.0. The alkali metal content of the finished 
catalyst should be less than about 1 and preferably less than about 0.5 
percent by weight. The cation-exchange solution can be contacted with the 
crystalline aluminosilicate of uniform pore structure in the form of a 
fine powder, a compressed pellet, extruded pellet, spheroidal bead or 
other suitable particle shapes. Desirably, the zeolite comprises from 
about 3 to about 60, preferably from about 10 to about 40, and more 
preferably from about 20 to about 40 wt % of the total catalyst inventory. 
The zeolite is preferably incorporated into a matrix. Suitable matrix 
materials include the naturally occurring clays, such as kaolin, 
halloysite, sepiolite, saponite, montmorillonite, pillared or cross-linked 
clays, and inorganic oxide gels comprising amorphous catalytic inorganic 
oxides such as silica, silica-alumina, silica-zirconia, silica-magnesia, 
alumina-boria, alumina-titania, and the like, and mixtures thereof. 
Preferably the inorganic oxide gel is a silica-containing gel, more 
preferably the inorganic oxide gel is an amorphous silica-alumina 
component, such as a conventional silica-alumina cracking catalyst, 
several types and compositions of which are commercially available. These 
materials are generally prepared as a co-gel of silicon and alumina, 
co-precipitated silica-alumina, or as alumina precipitated on a pre-formed 
and pre-aged hydrogel. In general, silica is present as the major 
component in the catalytic solids present in such gels, being present in 
amounts ranging between about 55 and 100 wt. %. The matrix component may 
suitably be present in the catalyst of the present invention in an amount 
ranging from about 40 to about 92 wt. %, preferably from about 60 to about 
80 wt %, based on the total catalyst. 
Especially preferred as the catalytically active component of the catalyst 
system claimed herein is a crystalline aluminosilicate, such as defined 
above, dispersed in a refractory metal oxide matrix, for example, as set 
forth in U.S. Pat. No. 3,944,482 to Mitchell et al., referred to above. 
The matrix material in the host catalyst can be any wellknown heat-stable 
or refractory metal compounds, for example, metal oxides, such as silica, 
alumina, magnesia, boron, zirconia, or mixtures of these materials or 
suitable large pore clays, acid activated clays, pillared or crosslinked 
clays or mixed oxide combinations. 
The particular method of forming the catalyst matrix does not form a part 
of this invention. Any method which produces the desired cracking activity 
characteristics can suitably be employed. Large pored refractory metal 
oxide materials suitable for use as a matrix can be obtained as articles 
of commerce from catalyst manufacturers or they can be prepared in ways 
well known in the art such as described, for example, in U.S. Pat. No. 
2,890,162, the specification of which is incorporated herein by reference. 
The method of forming the final composited catalyst also forms no part of 
this invention, and any method well known to those skilled in this art is 
acceptable. For example, finely divided zeolite can be admixed with the 
finely divided matrix material, and the mixture spray dried to form the 
final catalyst. Other suitable methods are described in U.S. Pat. Nos. 
3,271,418; 3,717,587; 3,657,154; and 3,676,330; whose descriptions are 
incorporated herein by reference. The zeolite can also be grown in the 
matrix material if desired, as defined, for example in U.S. Pat. No. 
3,657,718 to Hayden et al., or U.S. Pat. No. 4,493,902 to Brown et al., 
referred to above. 
In combination with the latter "in-situ" zeolite particles, a catalytically 
inert porous material may also be present in the finished catalyst. The 
term "catalytically inert" refers to a porous material having 
substantially no catalytic activity or less catalytic activity than the 
inorganic gel component or the clay component of the catalyst. The inert 
porous component can be an absorptive bulk material which has been 
pre-formed and placed in a physical form such that its surface area and 
pore structure are stabilized. When added to an impure inorganic gel 
containing considerable amounts of residual soluble salts, the salts will 
not alter the surface pore characteristics measurably, nor will they 
promote chemical attack on the pre-formed porous inert material. Suitable 
inert porous materials for use in the catalyst of the present invention 
include alumina, kaolin, halloysite, titania, silica, zirconia, magnesia, 
and mixtures thereof. The porous inert material, when used as a component 
of the catalyst of the present invention, is present in the finished 
catalyst in the amount ranging from about 10 to about 60 wt % based on the 
total catalyst. 
The Additive 
The additive defined herein is a separate and distinct particulate entity 
from the catalyst, and comprises two different components. The additive is 
preferably held together by a binder to impart structural integrity. These 
components each bring their own characteristics and qualities to the 
invention, and interact synergistically to yield an additive of unique 
properties. 
The first component comprises a magnesium-containing material, preferably a 
hydrous magnesium silicate, which may act as a matrix for the diluent, 
providing the medium for the active component to disperse within the 
additive itself. The preferred magnesium-containing compounds comprise 
hydrous magnesium silicate, more preferably sepiolite, (most preferably 
Spanish sepiolite), attapulgite, palygorskite, saponite, talc, and Celkate 
T-21.RTM., a synthetic amorphous magnesium silicate. It is preferred that 
the magnesium compound be in crystalline form, and low in both iron, 
potassium and sodium. 
The second component comprises a calcium-containing material, in particular 
a calcium and magnesium containing material, which, under conditions found 
in catalytic cracking processes, in combination with the first, transforms 
into active components which may consist of, but are not limited to 
periclase, and such calcium-magnesium silicates as merwinite, akermanite 
and to a lesser extent diopside. This second component is the active 
component of the additive and particularly provides the necessary vanadium 
trapping activity appropriate to the effectiveness of the present 
invention. 
The preferred calcium-containing materials comprise dolomite, 
calcium-magnesium silicate, calcium-magnesium oxide, calcium-magnesium 
acetate, and calcium-magnesium carbonate or subcarbonate. The most 
preferred material is dolomite. It is preferred that the 
calcium-containing materials be fine ground to a particle size of about 3 
microns or less in order to improve particle integrity, thereby increasing 
attrition resistance and to improve sulfur tolerance. 
The combination of the calcium-containing material and the 
magnesium-containing material and, in particular, the combination of 
dolomite and sepiolite, provides an additive with a high calcium-magnesium 
composition, which is particularly effective for vanadium trapping and 
which is at the same time attrition resistant and not so friable as to 
create process difficulties in catalytic cracking units. Moreover, the 
minerals involved, in particular dolomite, are relatively inexpensive, 
particularly relative to the zeolite component of the catalyst generally, 
thereby providing an economic advantage in view of the vanadium trapping 
efficiency of the additive. 
The ratio of the two components one to the other is also a factor in the 
effectiveness of the additive. It is preferred that the calcium-containing 
material and the magnesium-containing material be present in a weight 
ratio of from about 20:80 to about 80:20 calcium-containing material to 
magnesium-containing material. More preferably, the ratio is from about 
50:50 to about 70:30. 
It is preferred that the additive contain antimony or bismuth metallic 
passivators as heretofore described, e.g., U.S. Pat. No. 4,784,752, to 
assist the restoration of catalyst activity. It is preferred that the 
level of bismuth or antimony range from 0.05:1 to 1:1 atom to atom ratio 
of introduced passivator to nickel contaminant on the catalyst. 
While the specific mechanism by which the additive traps contaminants is 
not claimed as part of the present invention, one possible mechanism is 
suggested as follows. When fresh hydrocarbon feed contacts catalyst in the 
cracking zone, cracking and cooking reactions occur. At the same time, 
vanadium and nickel are quantitatively deposited on the surface of the 
catalyst. At this point the contaminant metals function by quite different 
mechanisms. Spent catalyst containing the metal deposits passes from the 
cracking unit to the regenerator where temperatures normally in the range 
of 1150.degree.-1400.degree. F. (621.degree.-760.degree. C.) are 
encountered in an oxygen/steam-containing environment. Conditions are 
therefore suitable for vanadium migration to and reaction with the active 
zeolitic component of the catalyst. The reaction results in formation of 
mixed metal oxides containing vanadium which causes irreversible 
structural collapse of the crystalline zeolite. Upon degradation, active 
sites are destroyed and catalytic activity declines. Activity can be 
maintained only by adding large quantities of fresh catalyst at great 
expense to the refiner. 
It is theorized that addition of the additive of the present invention 
prevents the vanadium interaction with the zeolite by acting as a trap or 
sink for vanadium. Under regenerating conditions, vanadium present on the 
catalyst particles preferentially migrates to and reacts with the 
calcium/magnesium-containing additive. Competitive reactions are occurring 
and the key for successful vanadium transfer is to utilize an additive 
with a significantly greater rate of reaction toward vanadium than that 
displayed by the zeolite. As a result, the vanadium is deprived of its 
mobility, and the zeolite is protected from attack and subsequent 
collapse. It is believed that vanadium and the calcium/magnesium additive 
forms one or more new binary oxides. 
In contrast to vanadium which is mobile, contaminant nickel is a relatively 
stationary phase, and poisons the catalyst in a different manner. Under 
the reducing environment of reactor conditions at typical temperatures of 
900.degree. to 1050.degree. F., nickel becomes an active dehydrogenation 
agent, forming excess coke and hydrogen at the expense of desirable 
gasoline yield. Activity of nickel for this competitive side reaction is 
dependent upon its degree of dispersion, which in turn is related to the 
surface area and porosity of the catalyst matrix. The effect of nickel can 
decay via the formation of large crystallites on the surface 
(agglomeration), formation of inert species with the matrix (spinels or 
silicates) or through the use of added passivators such as bismuth or 
antimony. 
It is postulated that the additive of the current invention deactivates the 
active nickel species by providing a reservoir of passivating bismuth or 
antimony. Under cracking conditions, a small but finite amount of 
passivator will proceed by a particle transfer mechanism to migrate to the 
offending nickel which it subsequently neutralizes by coating, alloying, 
or promoting agglomeration. 
The catalyst particle size must render it capable of fluidization as a 
disperse phase in the reactor. Typical and non-limiting fluid catalyst 
particle size characteristics are as follows: 
______________________________________ 
Size (Microns) 
0-20 20-45 45-75 &gt;75 
wt. % 0-5 10-15 45-65 20-40 
______________________________________ 
These particle sizes are usual and are not peculiar to this invention. The 
additive particle size is selected to assist physical separation from the 
catalyst without substantial loss of catalyst by, for example, selecting 
an additive particle size distribution centered around 20 microns or 
smaller, or conversely greater than 150 microns. 
Binder 
It is also preferred to include a separate binder which binds together the 
subcomponents of the additive. The binder provides additional strength and 
attrition resistance, as well as surface area and dispersion known to 
capture vanadium or other metals, i.e., large porosity. The preferred 
embodiment of the present invention would include from 5 to 30% by weight 
of an inorganic binder. The binder is used to impart density and strength 
and maintain particle integrity of the second component as is used in 
combination with the other components of the additive particle. The 
inorganic binder can be those conventionally employed by those skilled in 
the art, including but not limited to clays such as kaolin, bentonite 
(montmorillonite), saponite and hectorite, pillared or cross-linked clays, 
or precipitated synthetic binders such as alumina, zirconia, titania, 
silica, silica-alumina, or derived from such standard commercially 
available materials as Catapal.RTM., Chlorohydrol.RTM., or SMM.RTM., or 
combinations thereof. For application in high sulfur feeds, a preferred 
binder would be a sulfur trapping material such as alumina which might be 
obtained through the polymerization of Chlorohydrol.RTM. or peptized 
pseudo-boehmite alumina. 
A preferred method of preparing the additive is by spray-drying a slurried 
mixture of the components of the additive, including the binder. The 
slurried mixture may be prepared by, for example, adding the 
calcium-containing material and the magnesium-containing material to a 
silica sol, to peptized alumina, or to a mixture thereof. Peptized alumina 
may also be added to the slurried mixture after the other components of 
the additive are blended together. In the preferred embodiment, the 
concentrations of the components in the additive can range from a ratio by 
weight of 20%:80% to 80%:20% dolomite:sepiolite, with the binder 
comprising between about 5% to 20% by weight. The most preferred 
composition comprises 50% dolomite, 40% sepiolite and 10% binder. 
Demetallization of FCC Catalyst 
In the process of this invention, one begins with an FCC catalyst 
contaminated with metals, in particular, metals selected from the group 
consisting of vanadium, nickel and iron which deactivate the cracking 
catalyst. Contamination occurs in the course of FCC processing of heavy 
hydrocarbonaceous oils of high metals content. The extent of such metals 
contamination, expressed in terms of vanadium on the catalyst at 
equilibrium may range from about 2,000 to 10,000 ppm by weight or more, 
often between about 3,000 to 5,000 ppm, based on the weight of the 
catalyst. Expressed in terms of nickel equivalents where, 
EQU Ni equivalent=Ni+V/5+Cu/10+Fe/10, 
equilibrium metals may range from 1500 ppm to 10,000 ppm, and more often 
between 2,000 to 4,000 ppm, based on weight of catalyst. 
The vanadium content of the catalyst is reduced by contacting the catalyst 
with the additive of this invention under FCC process conditions, 
particularly, under the regenerating conditions of an FCC process. Such 
regenerating conditions comprise, generally, an oxidative atmosphere at 
high temperature. The temperature normally ranges from about 1150.degree. 
F. to 1500.degree. F., preferably from 1250.degree. F. to 1400.degree. F. 
FCC process regenerating conditions also comprise steaming of the catalyst 
in the presence or in the substantial absence of oxygen. Steam normally 
comprises 10 to 20% of the partial pressure of the FCC regenerators. If 
the metal contaminated catalyst is downloaded from the FCC regenerator, it 
can be rejuvenated by employing an external reactor at temperatures from 
1200.degree. to 1400.degree. F. at steam partial pressures ranging from 10 
to 95% of the total reactor pressure to enhance the mobility of the 
vanadium. 
The regenerating conditions comprise not only the normal FCC regeneration 
zone, but a separate fluidized bed under regenerating conditions may be 
used with the additive of this invention to demetallize FCC catalyst taken 
from the FCC unit via a slipstream. Alternatively, an ebullated bed 
reactor may be used. 
Preferably, the additive contains an antimony or bismuth compound, 
preferably antimony oxide or bismuth oxide, most preferably bismuth oxide. 
These compounds serve to passivate the metals on the FCC catalyst under 
cracking conditions, particularly, nickel, rendering a catalyst of 
increased gasoline selectivity, with reduced dehydrogenation and coking 
tendencies. 
After demetallization and/or passivation, the FCC catalyst may be 
optionally separated from the additive. Any means of separation known to 
the art may be used, but since both the FCC catalyst and the additive are 
particulate, separation by particle size differentiation is effective. Any 
means of particle size differentiation may be used, such as screening with 
appropriate mesh sizes. Alternatively, magnetic separation may be used. In 
particular, high intensity magnetic separation may be employed. To enhance 
the separation, it is suggested that a magnetic reactive component, for 
example iron oxide, be incorporated in the additive. 
In the preferred use of the present invention, the additive is added to the 
catalyst inventory of an FCC process unit in an amount of from about 1 to 
20% by weight of catalyst. The additive circulates with the FCC catalyst 
under FCC process conditions and serves as an in situ means of 
demetallizing the catalyst. 
In an alternative mode of operation, spent downloaded catalyst can be 
charged to an external reactor containing 10-40% of additive. Reaction 
conditions should be 1200.degree. to 1400.degree. F., 10-95% steam, 1-3% 
excess air. 
EXAMPLES 
Additive A 
Preparation of Dolomite/Sepiolite Additive 
A calcium/magnesium-containing material useful for this invention was 
prepared using an aluminum hydroxy oligomer as the binding agent. 80 g of 
a 50 wt % aqueous solution of aluminum chlor-hydroxy (Reheis Chemical) was 
dispersed in 500 ml of deionized water. To this was added 160 g (dry 
basis) of crushed Spanish sepiolite (Tolsa) with high shear, followed by 
200 g crushed dolomite again with high shear. The mixture thickened and 
was diluted back to about 36% solids by the addition of 150 ml of 
additional water, and allowed to stir for two hours at ambient conditions. 
The resultant slurry was then converted to microspheroidal form using a 
laboratory sized spray-drier (Yamato). The powder was dried at 250.degree. 
F. in a vacuum oven, and then reslurried in one liter of 20% ammonium 
hydroxide solution for 15 minutes at 80 C. The slurry was filtered and the 
process repeated. Resultant filter cake was further water washed and dried 
at 250.degree. F., and subsequently calcined at 1000.degree. F. the 
material was lightly crushed to break additives and sieved to 100/325 mesh 
and designated Additive A. A similar formulation was prepared in larger 
quantities using a Bowen pilot-plant sized spray-drier and designated 
Additive A'. These additives were comprised of 50% dolomite, 40% sepiolite 
and 10% binder, and on an oxide basis contained about 29 wt % calcium, 29 
wt % magnesium, and 32 wt % silicon. 
Additive B 
Alternative Preparation of Dolomite/Sepiolite Additive 
Another version of the calcium magnesium-containing material of the current 
invention was prepared using a higher level of a different precipitated 
silica-alumina binder. The specific formulation was 80 wt % active 
components (50:40 parts by weight dolomite:sepiolite) and 20 wt % binder 
(36:64 parts by weight of alumina:silica). On a 100 lb. dry basis, the 
formulation can be computed as using 44.4 lb. dolomite, 35.6 lb. 
sepiolite, 12.8 lb. silica, 7.2 lb. alumina and 1.45 lb. 90% formic acid. 
The active components -- dolomite and sepiolite -- were dispersed into a 
silica-alumina gel prepared by first peptizing a 12 wt % solids alumina 
(CATA) slurry with 90% formic acid at a 0.2 lb. acid/lb. alumina ratio, 
which was then added to a 40 wt % solids silica sol (Nalco 1027). To 
ensure both good particle attrition resistance and sulfur tolerance, 
finely ground, micronized dolomite and sepiolite clays were used. The 
dolomite (National Mineral Products, Grade D-307) was further comminuted 
to less than 3 microns average particle size by wet milling at about 35 wt 
% solids. The sepiolite (Tolsa, MICRO 65) was used as received. The order 
of addition was to add the micronized dolomite slurry to the binder 
slurry, followed by dry addition of the powdered sepiolite. High shear 
stirring was avoided to minimize gel formation. The system employed 
sufficient process water to produce a final make-down slurry of 28 wt % 
solids. The additive slurry was spray-dried to a coarser average particle 
size (&gt;90 microns) to help provide better retention in circulating 
fluidized beds. 
CATALYSTS 
A number of catalyst systems containing the additive used in the claimed 
process are described to demonstrate utility for vanadium passivation. The 
catalyst inventory of each test catalyst system (except for reference 
catalysts) contained a mixture of commercial catalyst particles, along 
with discrete, vanadium passivator particles. 
CATALYST 1 
Reference Catalyst 1 was a low metals, equilibrium version of OCTACAT "+", 
a commercial FCC catalyst manufactured by Davison Chemicals. It was 
calcined for 3 hours at 1300.degree. F. to burn off contaminate coke. 
CATALYST 2 
Catalyst 2 is physical blend of 80 wt % OCTACAT "+" calcined equilibrium 
(i.e., Catalyst 1) and 20 wt % Additive B. Additive B in this instance was 
calcined at 1500.degree. F. for three hours and sieved to 100/300 mesh. 
CATALYST 3 
Catalyst 3 is Catalyst 1 which had been contaminated with a nominal 6000 
ppm vanadium by circulating in a large 0.5 bbl/day pilot-plant with a 
vanadium naphthanate feedstock. 
CATALYST 4 
An admixture was prepared using 80 wt % Catalyst 1 with 20 wt % of Additive 
A'. The blend was subsequently contaminated with a nominal 6000 ppm 
vanadium loading in a manner analogous to Catalyst 3. 
CATALYST 5 
A blend of 90 wt % Catalyst 3 and 10% Additive A'. 
CATALYST 6 
A blend of 90 wt % Catalyst 4 and 10% Additive A'. 
Portions of Catalysts 1, 3, 4, 5, and 6 were each subjected to steam 
deactivation in a fluidized bed steaming unit at 1350.degree. F., and 20% 
steam at time intervals of 0, 48 and 72 hours, respectively. Catalysts so 
treated are identified with the suffix A, B, or C for 0, 48 or 72 hrs, 
respectively. Catalyst 6 which was steamed for 72 hour is designated as 
catalyst 6C. 
CATALYST 7 
Catalyst 7 was formulated by diluting a very high USY zeolite containing 
microspheroidal material stabilized with 1 wt % rare earths, to a net 34% 
USY. The diluent was an inert material having little catalytic or 
passivation activity. Both the zeolite concentrate and diluent materials 
were steam deactivated for 5 hours at 1475.degree. F., in a 
fixed-fluidized bed steamer, prior to blending. 
CATALYST 8 
A catalyst similar to Catalyst 7 was formulated to include 20 wt % of 
Additive B which had been steam deactivated for the equivalent of 1/2 hour 
at 1500.degree. F. and 50% steam. Additive B substituted for a portion of 
the diluent used in Catalyst 7. Net zeolite content of the catalyst was 
also 34%. 
EXAMPLE 1 
Selective Scavenging of Aged Vanadium 
A portion of Catalyst 2, a composite of calcined equilibrium catalyst and 
20% calcined Additive B of this invention, was steam-aged for 5 hours at 
1350.degree. F. in a flowing stream of 95% steam and 5% nitrogen. Both the 
steamed and unsteamed catalyst blends were then examined by Scanning 
Electron Microprobe techniques to determine vanadium concentrations on 
individual catalyst or additive particles. The results are listed in Table 
I, and are, reported as a ratio of the vanadium found on the steamed 
particles to the vanadium on the original unsteamed particles. The data 
indicate that the average majority host OCTACAT particle lost about 80 ppm 
vanadium when steamed in the presence of the vanadium trap, while the trap 
picked up typically about 350 ppm per particle, nearly 10 times its 
original level. The net gain in vanadium content by all particles of 
Additive B is computed to be 90% of the observed loss for the host 
equilibrium catalyst, reasonably good agreement given the low level of 
contamination and accuracy of the test method. Thus it can be seen that 
under the steaming conditions described, Additive B was able to 
selectively scavenge vanadium from the host FCC catalyst. 
EXAMPLE 2 
The beneficial effect of the additive of this invention in the presence of 
high vanadium contamination is demonstrated in Table III. Catalyst 3, the 
unprotected host FCC equilibrium material, and Catalyst 4 containing 20% 
of Additive A', were each loaded to a nominal 6000 ppm in a circulating 
fluid bed pilot-plant using a vanadium doped feed. They are contrasted 
with Catalyst 1, the vanadium free catalyst. A portion of each of the 
catalysts was aged at simulated regeneration conditions under which 
vanadium is known to migrate (1350.degree. F., 20% steam for 72 hours). 
Each of the catalysts was subsequently tested in a MAT test at 960.degree. 
F., 15 weight hourly space velocity (WHSV), 75 seconds contact time, and a 
catalyst to oil ratio (C/O) of 3.4 with 3.5 grams of catalyst. The charge 
stock was a gas-oil having a boiling range as characterized in Table II 
below. 
The poisoning effect of vanadium on the unprotected catalysts can be seen 
by comparing catalysts 1 and 3 at equivalent steaming times. Conversion 
and gasoline yield are lost due to degradation of the active zeolite 
component. Increased hydrogen make due to vanadium's ability to function 
as a dehydrogenation agent is also evident. The positive impact of having 
the vanadium scavenger present is seen by comparing catalyst 4 with 
catalyst 3. Much of the fresh conversion and gasoline yield is preserved 
and there is less of an effect of steaming. Likewise the dehydrogenation 
activity is diminished. 
EXAMPLE 3 
Having demonstrated that the synergistic dolomite/sepiolite combination 
provides passivation in the presence of freshly added vanadium, it remains 
now to be shown that the addition of fresh additive will remove previously 
deposited vanadium from an equilibrium catalyst. Evidence for this is 
tabulated in TABLE IV. Catalyst 5 is Catalyst 3 having a nominal value of 
6000 ppm vanadium-on-cat, to which has been added 10% fresh Additive A'. A 
portion of each catalyst was then further steamed for 48 or 72 hours. 
MAT evaluations show the dilution effect of adding the catalytically inert 
additive in the absence of further ageing. With additional steaming it can 
be seen Catalyst 5 retains more of its initial conversion and gasoline 
yield than does Catalyst 3. Likewise, Catalyst 5 has reduced hydrogen and 
coke make as compared to Catalyst 3, indicating vanadium passivation. The 
vanadium trapping ratio (vanadium on additive particle relative to 
vanadium on FCC catalyst particle) for Catalyst 5, as determined by 
electron microprobe inspections of the spent catalyst, is also consistent 
with the data. Steaming is the driving force that provides mobility for 
deposited vanadium at regenerator temperatures. As steaming time increases 
the vanadium trapping ratio is climbing, indicating selective scavenging 
and retention of vanadium by Additive A". Thus, this data confirms the 
effect observed in Example 1, namely that the additive can cleanse an 
equilibrium catalyst of aged vanadium. 
EXAMPLE 4 
Additional evidence of the ability of Additive A' to passivate FCC 
catalysts by extracting aged vanadium is depicted in Table V. In this 
instance 10% of fresh Additive A' has been added to Catalyst 4 which 
already contains a blend of 20% additive and has been contaminated with 
6000 ppm vanadium. As steaming time progresses, both catalysts are 
exhibiting vanadium passivation, but at the end of 72 hours, Catalyst 6C 
which contains 50% more additive (hence more activity dilution) is 
providing comparable conversion and reduced hydrogen and coke selectivity. 
Moreover, the vanadium trapping ratio has been growing consistently. After 
72 hours, each additive particle contains nearly 18 times the vanadium 
loading as the host FCC particle. The nearly threefold increase in 
trapping ratio over the previous example is attributed to a threefold 
increase in additive content, and also indicates that both fresh and aged 
additive are continuing to provide passivation. 
EXAMPLE 5 
The additive of this invention was tested for its ability to passivate 
vanadium in the presence of high levels of nickel. Catalysts 7 (Reference) 
and 8 (with additive) were formulated to the same net zeolite content 
using rare earth stabilized USY from previously steam deactivated 
materials. Each was subsequently contaminated with approximately 3000 ppm 
nickel equivalents (Nickel Equivalent=Ni, ppm+V/5, ppm) by cracking in a 
fixed-fluidized bed cyclic (FFBC) reactor using a feedstock doped with 
nickel and vanadium naphthanates. This testing methodology is designed to 
mimic pilot-plant and commercial FCC operating conditions. It permits the 
catalyst inventory to be exposed to a repetitive cyclic environment 
consisting of cracking, steam stripping, and regeneration. 
Two different sets of ageing conditions were employed, viz: 
* C1: Ageing occurred over 70 cycles, with cracking at 16 WHSV and 
1030.degree. F., steam stripping at 970.degree. F., and regeneration at 
1400.degree. F. in the presence of 50% steam. This set of conditions is 
known to produce a catalyst having a metals distribution profile 
resembling a true commercial equilibrium catalyst. 
* C2: An accelerated sequence where ageing time is reduced to 20 cycles at 
8 WHSV, but regeneration severity is increased to 1450.degree. F. 
Each of the aged catalysts was MAT tested using Feedstock 2, having those 
properties as listed in Table VI. Results of the Catalytic evaluations are 
presented in Table VII. Vanadium and nickel levels are cited for each 
catalyst and are close to the target value. Under both sets of conditions, 
Catalyst 7, the unprotected catalyst, is substantially deactivated, with 
respect to Catalyst 8 containing the vanadium trap. Under test C1, 
Catalyst 8 is approximately 30% more active, and shows a significant gain 
in gasoline yield, coupled with a simultaneous improvement (i.e., 
reduction) in hydrogen and coke selectivity. Under the milder conditions 
of test C2, Catalyst 8 is still 16% more active than the reference with 
similar directional improvements in yield pattern. Reduction of vanadium's 
dehydrogenation activity is still apparent, albeit less extensive because 
deposited vanadium has less opportunity to migrate and poison the 
catalyst. Thus, the effectiveness of the instant dolomite/sepiolite 
additives for enhanced specificity for vanadium, even in the presence of 
nickel, has been demonstrated. 
TABLE I 
______________________________________ 
Catalyst: 2 
Average Vanadium Content, ppm 
Particle: OCTACAT Additive B 
______________________________________ 
Fresh 280 40 
Steamed: 200 390 
Gain (Loss) (80) 350 
Ratio: V Steamed/V Fresh 
0.71 9.8 
______________________________________ 
TABLE II 
______________________________________ 
Gas Oil Inspections 
Stock 
Identification Feedstock No. 1 
______________________________________ 
Inspections: 
Gravity 27.4 
Nitrogen, wt % 0.10 
Basic Nitrogen, ppm 
244 
Pour Point 33 
Aniline Point, .degree.F. 
187.3 
Distillation, D 1160 Dist. 
Start 444.degree. F. 
10 Pct. Cond. 607.degree. F. 
30 pct. Cond. 707.degree. F. 
50 Pct. Cond. 784.degree. F. 
70 Pct. Cond. 867.degree. F. 
90 Pct. Cond. 979.degree. F. 
EP 1046.degree. F. 
______________________________________ 
TABLE III 
______________________________________ 
Catalyst 1A 1C 3A 3C 4A 4C 
______________________________________ 
Additive B, wt % 
-- -- -- -- 20 20 
Vanadium, ppm 
0 0 6000 6000 6000 6000 
Steaming, hrs. 
0 72 0 72 0 72 
Zeolite unit cell 
24.26 24.25 24.25 
24.25 24.25 
24.25 
size, .ANG. 
Conversion, wt % 
70 64 59 54 63 59 
Activity 2.33 6.77 1.43 1.17 1.70 1.43 
Yield, wt % 
C5-430 50 47 44 40 47 45 
H2 0.076 0.127 0.389 
0.495 0.149 
0.233 
Coke 2.96 2.51 0.176 
2.08 2.64 2.62 
______________________________________ 
TABLE IV 
__________________________________________________________________________ 
Catalyst 3A 5A 3B 5B 3C 5C 
__________________________________________________________________________ 
Vanadium, ppm Nominal 
.rarw. 6000 .fwdarw. 
Fresh Additive, % 
-- 10 -- 10 -- 10 
Steaming, hrs. 
0 0 48 48 72 72 
Conversion, wt % 
59 55 54 54 54 54 
Activity 1.43 1.22 1.17 1.17 1.17 1.17 
Yield, wt % 
C5-430 44 42 41 40 40 41 
H2 0.389 
0.334 
0.564 
0.382 
0.495 
0.350 
Coke 1.76 2.13 2.05 1.69 2.08 1.51 
Selectivity* 
C5-430 0.75 0.76 0.76 0.74 0.74 0.76 
H2 0.0066 
0.0061 
0.0104 
0.0071 
0.0092 
0.0065 
Coke 0.0298 
0.0387 
0.0380 
0.0313 
0.0385 
0.0280 
Vanadium Additive/Vanadium FCC 
0.10 5.7 6.8 
__________________________________________________________________________ 
*Yield per unit conversion 
TABLE V 
______________________________________ 
Catalyst: 
4A 6A 4B 6B 4C 6C 
______________________________________ 
Fresh 0 10 0 10 0 10 
Additive A 
Steaming hrs. 
0 0 48 48 72 72 
Conversion, 
63 61 60 58 59 59 
wt % 
Activity 1.70 1.56 1.50 1.38 1.43 1.43 
Yield, wt % 
C5-430 47 46 45 44 45 44 
H2 0.149 0.151 0.264 0.164 0.233 0.133 
Coke 2.64 3.18 2.77 2.35 2.62 2.24 
Selectivity:* 
C5-430 0.75 0.75 0.75 0.76 0.76 0.75 
H2 0.0024 0.0025 0.0044 
0.0028 
0.0039 
0.0023 
Coke 0.0419 0.0521 0.0461 
0.0405 
0.0444 
0.0380 
Vanadium Additive/ 
7.7 15.8 17.4 
Vanadium FCC 
______________________________________ 
*Yield per unit conversion 
TABLE VI 
______________________________________ 
Gas Oil Inspections 
Stock Identification 
Feedstock No. 2 
______________________________________ 
Inspections: 
Gravity 24.3 
Nitrogen, Wt % 0.10 
Basic Nitrogen, ppm 
210 
Sulfur, Wt % 0.33 
RAM Carbon 0.17 
Aniline Point, .degree.F. 
185.8 
Distillation, D 1160 Dist. 
10 Pct. Cond. 703.degree. F. 
30 Pct. Cond. 795.degree. F. 
50 Pct. Cond. 872.degree. F. 
70 Pct. Cond. 961.degree. F. 
90 Pct. Cond. 1098.degree. F. 
EP 1256.degree. F. 
______________________________________ 
TABLE VII 
______________________________________ 
Catalyst 7 8 7 8 
Test C1 C1 C2 C2 
______________________________________ 
Vanadium, ppm 
4700 3770 3990 4260 
Nickel, ppm 2700 2200 2360 2340 
Conversion, wt % 
58 65 59 63 
Activity 1.37 1.81 1.44 1.67 
Yield, wt % 
C5-430 42 47 43 46 
H2 0.97 0.76 0.98 0.92 
Coke 5.83 5.61 6.02 6.26 
Selectivity* 
C5-430 0.74 0.73 0.73 0.72 
H2 0.0169 0.0117 0.0166 0.0143 
Coke 0.1012 0.0871 0.1022 0.0969 
______________________________________ 
*Yield per unit of conversion