Catalyst

The invention provides a catalyst composition useful in treating hydrocarbons contaminated with vanadium residues, the catalyst comprising a zeolite, a matrix and certain heavier alkaline earth metal oxides.

FIELD OF THE INVENTION 
The invention relates to cracking catalysts and to catalytic cracking, 
which is a major refinery process for the conversion of hydrocarbons to 
lower boiling fractions. More specifically, the invention relates to 
catalyst compositions which are particularly resistant to degradation by 
vanadium deposited on the catalyst in the course of the cracking reaction, 
and to an improved process for cracking vanadium containing feedstocks by 
using these catalysts. 
BACKGROUND OF THE INVENTION 
Catalysts containing crystalline zeolites dispersed in an inorganic oxide 
matrix have been used for the catalytic cracking of petroleum-derived 
feedstocks for many years. During this time, it has been widely recognised 
in the industry that certain contaminants (notably vanadium, nickel, and 
iron), initially dissolved or dispersed in the hydrocarbon feedstock, are 
deposited on the catalyst during the catalytic cracking process, and the 
accumulated deposits lead to undesirable changes in the activity and 
selectivity of the thus contaminated catalysts. Typically, the harmful 
effects noted have been increased yields of coke and hydrogen, a 
phenomenon ascribed to the action of the deposited metals as centres of 
dehydrogenation. More recently, however, it has been appreciated that 
vanadium also has other harmful properties, as well as increasing 
dehydrogenation activity, it reacts with and destroys the zeolite 
component of the catalyst, leading to a severe decrease in the activity of 
the catalyst. 
These problems have become more acute as refiners have faced the need to 
process heavier feedstocks which contain increased amounts of the metal 
contaminants, and various strategies have been employed to alleviate the 
deleterious effects and facilitate smooth running of catalytic cracking 
units. These approaches have included 
(1) more frequent replenishment of the circulating catalyst inventory; 
(2) withdrawal of the regenerated catalyst and treatment with various 
chemicals to passivate the metals; 
(3) changes in the design or operation of the catalytic cracker to reduce 
the poisoning activity of the contaminant metals; 
(4) addition to the feedstock of compounds of elements such as antimony, 
tin, barium, manganese, germanium and bismuth. 
Examples of these approaches will be found in the , following patents: U.S. 
4 111 845, U.S. 4 101 417, U.S. 4 377 494, U.S. 4 367 136, U.S. 3 977 963. 
Further attempts to cope with harmful effects of metals, especially 
vanadium, have related to modifications of the cracking catalyst itself; 
these have included admixture with sacrificial catalyst particles, careful 
control of the zeolite composition, and inclusion in the catalyst of 
specified amounts of vanadium trapping additives, including alumina, 
titanium dioxide (titania) and zirconium dioxide (zirconia) and certain 
compounds of calcium and magnesium. Disclosures of such catalysts will be 
found in US 4 432 890, US 4 451 355 and BE 899 446.

GENERAL DESCRIPTION OF THE INVENTION 
The present invention provides a catalyst composition comprising a (i) 
crystalline zeolite, (ii) a matrix material, and (iii) certain crystalline 
mixed oxides, derived from the heavier alkaline earth elements (calcium, 
strontium, barium) and certain combinations with elements of group IV of 
the periodic table, which oxides have themselves no harmful effects on the 
catalytic properties but are present in amounts sufficient to act as a 
vanadium passivator. 
Accordingly, the present invention provides a catalyst composition 
comprising (i) a crystalline zeolite, (ii) a matrix material and (iii) a 
mixed oxide selected from calcium, strontium and barium tin oxides and 
strontium and barium titanium oxides and mixtures thereof. 
The crystalline zeolite component of the present invention, which is 
usually present in the range from about 5% to about 40% by weight, may 
generally be described as a crystalline, three dimensional, stable 
structure enclosing cavities of molecular dimensions. Most zeolites are 
based on aluminosilicate frameworks, the aluminium and silicon atoms being 
tetrahedrally coordinated by oxygen atoms. However, for the purposes of 
our invention we include as "zeolites" similar materials in which atoms of 
other elements are present in the framework, such as boron, gallium, 
germanium, chromium, iron, and phosphorus. Further we include materials 
such as pillared interlayered clays ("PILCS"), which have many of the 
catalytically valuable characteristics of the aluminosilicate zeolites. We 
also include all modifications to the above materials, whether obtained by 
ion-exchange, impregnation, hydrothermal or chemical treatments. 
Zeolites which can be employed in the catalysts and processes of this 
invention can be natural or synthetic in origin. These naturally occurring 
zeolites include gmelinite, chabazite, dachiardite, clinoptilolite, 
faujasite, heulandite, analcite, levynite, erionite, sodalite, canorinite, 
mepheline, lazurite, scolecite, natiolite, offretite, mesolite, mordenite, 
brewsterite, fevierite, and the like. Suitable synthetic zeolites are 
zeolites A,B,E,F,H,J,L,Q,T,W,X,Y,Z, alpha, beta, omega, the EU types, the 
Fu types, the Nu types, the 2K types, the ZSM types, the ALPO types, the 
SAPO types, the L2 series, and other similar materials will be obvious. 
The effective pore size of the synthetic zeolites are preferably between 
0.6 and 1.5 nanometers, and the preferred zeolites are those with the 
faujasite framework and silica/alumina ratios &gt;3, thus including synthetic 
zeolite Y and the various form of Y which have been made more siliceous by 
chemical, hydrothermal or thermal treatments. 
In a preferred embodiment of the invention, the zeolite is converted to a 
form which is most applicable for catalytic cracking. In general this 
involves a sequence of ion-exchange and calcination treatments to 
introduce acid groups into the zeolite, stabilise the structure, and 
remove alkali metal cations. The preferred method of achieving this end, 
well known in the art, is to exchange the zeolite with solutions 
containing ammonium ions and/or rare earth ions (either a pure rare earth 
compound or a mixture). 
Such treatment can be carried out either on the zeolite before it is 
incorporated in the catalyst, or on the finished catalyst containing the 
zeolite, it can be carried out on a filter press, filter table, or filter 
belt, or by slurrying the zeolite/catalyst in a tank. 
The matrix into which the zeolite is incorporated can have a wide range of 
compositions. Suitable components include: naturally occurring or 
synthetic clays, including kaolin, halloysite and montmorillonite; 
inorganic oxide gels, including binary gels such as silica, 
silica-alumina, silica-zirconia, silica-magnesia, aluminium phosphates, or 
ternary combinations such as silica-magnesia-alumina; and crystalline 
inorganic oxides such as silica, alumina, titania, zirconia. 
Suitable mixed oxides for use as component (iii) are: 
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CaSnO.sub.3 
Ca.sub.2 SnO.sub.4 
SrTiO.sub.3 
SrTi.sub.12 O.sub.19 
Sr.sub.2 TiO.sub.4 
Sr.sub.3 Ti.sub.2 O.sub.7 
Sr.sub.4 Ti.sub.3 O.sub.10 
SrSnO.sub.3 
Sr.sub.2 SnO.sub.4 
Sr.sub.3 Sn.sub.2 O.sub.7 
BaTiO.sub.3 
BaTi.sub.2 O.sub.5 
BaTi.sub.4 O.sub.9 
BaTi.sub.5 O.sub.11 
Ba.sub.2 TiO.sub.4 
Ba.sub.2 Ti.sub.5 O.sub.12 
Ba.sub.2 Ti.sub.9 O.sub.20 
Ba.sub.4 Ti.sub.13 O.sub.30 
Ba.sub.6 Ti.sub.17 O.sub.40 
BaSnO.sub.3 
Ba.sub.2 SnO.sub.4 
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The mixed oxide additive is a discrete component of the final catalyst, and 
is readily identifiable in the fresh catalyst by x-ray diffraction 
analysis. These materials are insoluble, and are not decomposed into their 
component oxides over a wide range of thermal and hydrothermal treatments, 
and, as such are readily identifiable in hydrothermally deactivated 
catalyst samples. Preferably the mixed oxide is present at a level of 
least about 1% by weight of the catalyst and up to about 20% by weight. 
The chemical form of the additive is central to determining the 
concentration in which it is used in the catalyst composition, or indeed 
its method of incorporation into the catalyst formulation. 
It is a possibility that the alkaline earth mixed oxide additive reacts 
with vanadium on the catalyst through a displacement type reaction 
resulting in the formation of high melting point alkaline earth vanadates, 
thus immobilising the vanadium, and preventing its further reaction with, 
and destruction of the zeolite component of the catalyst, but there might 
also be another explanation. In this manner, the alkaline earth compound 
is involved in a competitive reaction for the vanadium with the zeolite. 
The alkaline earth compounds of this invention are successful as 
passivators as a result of their high reactivity towards vanadium compared 
to the zeolite. 
The use of crystalline mixed oxides containing titanium or tin, is to 
render the alkaline earth additive inert to catalyst processing 
procedures, and yet active in vanadium passivation on the final catalyst, 
thus producing catalysts of increased vanadium tolerance, with little or 
no adverse changes in catalytic and physical properties, when compared to 
conventional catalysts. 
Preferably, the concentration of the additive in the catalyst will be in at 
least 1:1 molar proportion of alkaline earth to vanadium with respect to 
the maximum vanadium level deposited on the catalyst during use. Thus, the 
concentration of the alkaline earth additive in the catalyst, can be 
tailored to best suit the process in which it is used, thereby allowing 
the operation of the catalytic cracking unit to be optimised. 
The additives of this invention can be prepared by various processes; for 
example, by calcination of intimate mixtures of the oxides or carbonates 
of the component elements, in the appropriate molar quantities, as 
disclosed by J Arjomand, J Less Common Met 61 133 1978, or by 
coprecipitation, or metathesis of salts of the appropriate elements. 
Conventional catalyst processing procedures encompass a wide range of pH 
conditions, typically pH 3 to pH 10, and require that any additives be 
resistant to such environments without themselves being decomposed, or 
resulting in changes in the properties of other catalyst components. The 
effect of additives not resistant to such environments can be to render 
the catalyst processing procedure inoperable, or to adversely affect both 
the physical and catalytic properties of the finished catalyst. 
As the form of the additives of the present invention are insoluble and 
inert to any catalyst processing procedures, the catalysts containing 
these additives may be prepared by any of the conventional methods used 
for the manufacture of FCC catalysts. For example, catalyst may be 
prepared by making an inorganic oxide sol at pH 3 and adding to this, 
aqueous slurries of the other catalyst components including zeolite and 
alkaline earth additive. The homogenised slurry can then be spray dried to 
produce catalyst microspheres, and washed free of soluble salts using for 
example aqueous ammonium sulphate and water. 
The catalyst compositions of this invention are employed in the cracking of 
vanadium containing heavy hydrocarbon feedstocks, to produce gasoline, and 
light distillate fraction. Typical feedstocks would have an average 
boiling point greater than 316.degree. C, and include such materials as 
gas oils, and residual oils. 
Because the catalysts of this invention are effective in cracking processes 
even when contaminated with vanadium to levels in excess of 5000 ppm, 
these catalysts can be used to process feedstocks containing significantly 
higher concentrations of vanadium than those employed in conventional 
catalytic cracking operations. 
These catalysts may be employed in any catalytic cracking process capable 
of operating with conventional microsphere fluid catalysts. 
SPECIFIC DESCRIPTION OF THE INVENTION 
The following examples illustrate the advantages of the invention. However, 
it is not intended that the invention be limited to the specific examples 
given. 
EXAMPLE 1 
A calcium stannate additive was prepared by mixing together, with constant 
agitation, a solution of 236g of Ca(NO.sub.3).sub.2.4H.sub.2 O, in 500g of 
deionised water, and a solution of 267g Na.sub.2 SnO.sub.3.3H.sub.2 O in 
500g of deionised water. The resulting precipitate was filtered, and 
washed repeatedly, until the filtrate was free of Na.sup.+. The filter 
cake was then dried at 100.degree. C., and finally calcined at 
1000.degree. C. for 4 hrs, to give crystalline CaSnO.sub.3 which was 
identified by X-ray diffraction. The crystalline CaSnO.sub.3 was finally 
finely ground prior to incorporation into the catalyst. 
The catalyst composition was prepared by combining together 75g Al.sub.2 
O.sub.3, 276g kaolin, 138g CaSnO.sub.3, and 165g CREY (Calcined Rare Earth 
Y zeolite), in 2175g of a silica sol (8% SiO.sub.2) at pH 3.2 to provide a 
homogeneous slurry. The slurry was then spray dried to form catalyst 
microspheres with an average particle size of 60 microns. 
The spray-dried catalyst was then washed with deionised water, ca 0.25M 
ammonium sulphate, and finally deionised water to remove sodium, until the 
conductivity of the filtrate fell below 1 milli mho. 
EXAMPLE 2 
The strontium titanate additive was prepared by grinding together 104g of 
SrCO.sub.3, and 80g of TiO.sub.2 to give a homogeneous mixture. The 
mixture was then calcined at 1000.degree. C. for 20 hrs to give 
crystalline SrTiO.sub.3 which was identified by X-ray diffraction. The 
crystalline SrTiO.sub.3 was finally finely ground prior to incorporation 
into the catalyst. 
The catalyst composition was prepared by combining together 100g Al.sub.2 
O.sub.3, 478g kaolin, 89g SrTiO.sub.3, and 219g CREY in 2871g of a silica 
sol (8% SiO.sub.2) at pH 3.2 to provide a homogeneous slurry. 
The slurry was then spray dried into microspheres of catalyst, and the 
catalyst finally washed according to the procedure in the previous example 
to remove soluble Na.sup.+ ions. 
EXAMPLE 3 
The barium titanate additive was prepared by grinding together 197g of 
BaTiO.sub.3, and 79.9g of TiO.sub.2 to give a homogeneous mixture. The 
mixture was then calcined at 1000.degree. C. for 16 hrs to give 
crystalline BaTiO.sub.3, which was identified by X-ray diffraction. 
The catalyst composition was prepared by combining together 100g Al.sub.2 
O.sub.3, 494g kaolin, 76g BaTiO.sub.3, and 219g CREY in 2850g of a silica 
sol (8% SiO.sub.2) at a pH of 3.2 to provide a homogeneous slurry. 
The slurry was then spray dried into microspheres of catalyst, and the 
catalyst finally washed according to the procedure in example 1, to remove 
soluble Na.sup.+ ions. 
EXAMPLE 4 (COMATIVE) 
A catalyst composition containing no alkaline earth mixed oxide additive 
was prepared by combining together 200g Al.sub.2 O.sub.3, 1164g kaolin, 
and 438g CREY, in 5966g of a silica sol (8% SiO.sub.2) at pH 3.2 to 
provide a homogeneous slurry. The slurry was then spray dried into 
microspheres, and finally washed according to the procedure in example 1 
to remove soluble Na.sup.+ ions. 
EXAMPLE 5 
A sample of catalyst of example 1. previously thermally treated to 
538.degree. C. for 2 hrs was impregnated with 5000 ppm vanadium according 
to the following procedure. 50g of the dried catalyst was slurried in 50 
ml of an aqueous solution containing 1.24g VOSO.sub.4 in a rotary 
evaporator. The slurry was allowed to fully mix for 30 mins at room 
temperature with constant agitation. The slurry was then dried under 
vacuum to yield the vanadium impregnated catalyst. The impregnated 
catalyst was finally calcined at 538.degree. C. for 2 hrs (Catalyst IM). 
EXAMPLE 6 
50g of catalyst of Example 2, thermally treated to 538.degree. C. for 2 hrs 
was impregnated with 5000 ppm V using the procedure detailed in example 5 
(Catalyst IIM). 
EXAMPLE 7 
50g of catalyst of Example 3, thermally treated to 538.degree. C. for 2 
hrs, was impregnated with 5000 ppm V, using the procedure detailed in 
example 5 (Catalyst IIIM). 
EXAMPLE 8 
50g of catalyst of Example 4, thermally treated to 538.degree. C. for 2 
hrs, was impregnated with 5000 ppm V, using the procedure detailed in 
example 5 (Catalyst IVM). 
The catalysts from the above examples were evaluated in a microactivity 
test (MAT) unit. Prior to testing, the catalyst samples were thermally 
treated at 538.degree. C. for 3 hrs and then deactivated in steam, at 
atmospheric pressure, at a temperature of 788.degree. C. (1450.degree. F.) 
for a period of 4 hrs. The cracking conditions used for the MAT were 
482.degree. C. (900.degree. F.), a space velocity of 16.0 WHSV and a 
catalyst to oil ratio of 3. The gas oil feed used in all of the tests was 
characterised as follows: 
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Gravity .degree.API 27.6 
Sulphur wt % 0.64 
Nitrogen wt % 0.09 
Carbon residue wt % 0.39 
Aniline point .degree.F. 
182.00 
Distillation .degree.F. 
10% at 760 mm Hg 574 
30% at 760 mm Hg 682 
50% at 760 mm Hg 773 
70% at 760 mm Hg 870 
90% at 760 mm Hg 991 
Initial Boiling Point 338 
Final Boiling Point 1061 
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TABLE 1 
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Catalyst No 
Wt % I II III IV 
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Conversion 75.5 76.3 76.2 75.3 
Gasoline 56.9 58.2 57.8 57.5 
LCO 15.2 14.7 14.4 15.7 
H.sub.2 0.08 0.033 0.046 0.019 
Coke 4.78 4.21 4.14 3.78 
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TABLE 2 
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Catalyst No 
Wt % IM IIM IIIM IVM 
______________________________________ 
Conversion 53.2 44.9 31.8 19.0 
Gasoline 43.1 36.3 25.1 12.9 
LCO 19.4 23.1 24.3 23.1 
H.sub.2 0.11 0.19 0.22 0.31 
Coke 2.83 2.58 2.17 3.14 
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Table 1 shows MAT results for catalysts (I-III) compared with catalyst (IV) 
containing no additive, demonstrating that the presence of the additives 
in the catalyst composition has no significant effect on either catalyst 
activity or selectivity, in that both conversion and gasoline yield are 
effectively unaltered by the addition of the additives, while coke and 
H.sub.2 yields are slightly increased. 
The performance of catalysts containing the alkaline earth additives of 
this invention, in the presence of vanadium show considerable benefits 
over catalysts containing no such additives, as can be seen by comparison 
of the results for catalysts (IM-IIIM) with catalyst (IVM) (Table 2) all 
in the presence of 5000 ppm Vanadium. These results show substantial 
improvements in vanadium tolerance for the catalyst compositions 
containing the additives as seen by higher conversion levels, improved 
gasoline selectivity, and reduced coke and hydrogen production.