FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
COMPLETE SPECIFICATION
[See Section 10 rule 13]

STABILIZED DUAL ZEOLITE SINGLE PARTICLE CATALYST
Process For Preparing
INDIAN OIL CORPORATION LIMITED, a public limited company having its head office at: G-9, Ali Yavr Jung Marg, Bandra (East), Mumbai 400 051, India.
The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed.
1

FIELD OF INVENTION
The present invention relates to a stabilized dual zeolite low coke forming single particle
catalyst, bonded with silica alumina binder, for cracking heavy residual hydrocarbons into lighter products. The present invention also relates to a process for the preparation of the stabilized dual zeolite catalyst.
BACKGROUND AND PRIOR ART OF THE INVENTION
Catalytic cracking today constitutes several refining processes in which heavier
hydrocarbons are cracked into lighter useful products. They are fluid catalytic cracking
(FCC), hydrocracking, reforming, etc. FCC process is simple and highly flexible as
required product slate can be obtained with varying feed properties.
The earliest catalysts used for fixed bed cracking were based on acid reacted clays. The exigencies imposed during the Second World War provided required acceleration to the concept and growth of moving bed catalytic cracking process. This process demanded more rugged catalysts than activated clays. Demand for this was met by more active silica alumina gel based synthetic catalysts, which provided an improved physical stability, and greater selectivity.
Grinding and screening methods were used to produce catalyst particles of required size. Later, spray drying technique produced catalyst particles of required size and with improved attrition resistance suitable for fluid bed reactor systems.
Introduction of silica-magnesia based matrix provided greater selectivity towards the production of middle distillates than silica-alumina based catalysts. One of the most significant developments in the area of cracking catalyst was the introduction of crystalline inorganic synthetic products called "Y zeolites".
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TheY zeolites having discrete pores in the range 6.5 to 13.5°A, higher surface area and higher acidity compared to the amorphous silica-alumina based catalysts generated higher catalytic activity and much more selectivity towards gasoline.
Later on, by employing rare earth exchanged Y zeolites and ultra stable Y zeolites many active and stable catalysts were developed.
Along with the introduction of highly stable cracking components like zeolites in different forms, in the past, there have been gradual improvements in binder system used for binding these crystalline materials into ttritioh resistant microspheres.
Use of silica sol based binder system in the preparation of zeolite promoted catalysts is cited in U.S. Pat. No. 3.867.308j and alum buffered silica-sol is described in U.S. Pat. No. 3,957,689.
Binding of low soda Y zeolite with gel alumina and polysilicate has been described in U.S. Pat. Nos. 4,333,857 and 4,326,993. s
vU.S. Pat. No. 4,987,110 refers to the preparation of attrition resistant FCC catalysts using low soda silica sol, REUSY and aluminum chlorohydrol.
Product selectivity of faujasite zeolite (also referred as Y zeolite) based catalysts is restricted to gasoline range molecules, due to the presence of uniform size large pores in the range 6.5°A and 13.5°A. For enhancing C3 to C4 selectivity, for first time ZSM-5 zeolites having pores in the range 5.4 to 5.5°A, were employed along with faujasite zeolites, in a conventional silica-alumina based binder system and process for this is described it 'U.S. Pat. No. 3,758,403.
U.S. Pat. No. 3,847,793 describes a process for conversion of hydrocarbons with a dual cracking component catalyst comprising ZSM-5 zeolite based catalyst and large pore zeolite based catalyst.
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U.S. Pat. No. 6,258,257\refers to a process for producing polypropylene from C3 olefins by a two-stage fluid catalytic cracking process having two types of catalysts made from zeolites of large pore and medium pore.
U.S. Pat.No.6,137,022: discloses a process of making an olefin product from an oxygenated feedstock by contacting the feedstock in a reaction zone containing 15 volume percent or less of a catalyst, preferably a catalyst comprising a silica-alumina-phosphate molecular sieve.
Another method of adding ZSM-5 to a moving bed catalytic cracking unit is disclosed in the published European Application No. EP 0167325A3> The make-up catalyst may contain 2 or 3 times the amount of ZSM-5 sought for the equilibrium catalyst.
1, U.S. Pat. No. 6,156,947 refers to a process for jointly producing butene-1 and ether in a catalytic distillation column, which comprises an upper catalytic zone for etherification and a lower catalytic zone for isomerization of C3 to C4 olefins and conversion of butadiene.
U.S. Pat. No. 5,997,728 refers to a process for catalytically cracking of a heavy feed in a FCC ukit. with large amounts of shape selective cracking additive. The catalyst inventory prefefably contains at least 10 wt% additive, of 12-40% ZSM-5 on an amorphous support, equivalent to more than 3.0 wt% ZSM-5 crystal circulating with equilibrium catalyst. This process yields large amount of light olefins, without excessive production of aromatics, or loss of gasoline yield.
U.S. Pat. No. 4,309,280 describes a process for maximizing of LPG by adding very small amounts of powdered, neat ZSM-5 catalyst, characterized by a particle size below 5 microns to ther CC catalyst inventory.
U.S. Pat. No. 5,190,902 rfefers to a process for the preparation of attrition resistant binder particles by spray drying of clay phosphate slurry with adjusted pH. At extreme pH conditions (pH above 12 and below 2), aluminum in clay is converted to AF+++" ions and on
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calcination in presence of phosphate ions, forms aluminum phosphate binder. This reaction condition is exploited in developing attrition resistant microspheres. It may be noted from the different examples that, clay-phosphate based binder is particularly suitable for zeolites with higher silica to alumina ratio and not suitable for binding low SiC>2 to AI2O3 ratio (ratio below 6) zeolites. This is due to the fact that, at lower pH conditions alumina of zeolite is also likely to get ionized and phosphate will not differentiate between alumina of clay and alumina of zeolite and react with both. This leads to the removal of alumina of zeolite framework, there by substantially reducing catalytic activity of the zeolite.
U.S. Pat. No. 5,286,369 describes a phosphate based binder composition suitable for
binding high silica zeolites. Here, reaction between aluminum nitrate and phosphoric acid
forms aluminum phosphate binder. However, during the reaction, along with the formation
of aluminum phosphate binder, nitric acid is also formed as a by-product as per following
reaction.
Al (N03)3 + H3PO4 -> AIPO4+ 3HN03
Presence of nitric acid is detrimental to the stability of Y zeolites due to dealumination.
Recent work on ZSM-5 additive has been directed at stabilizing the zeolite and also making the additive more attrition resistant. Phosphorus stabilized ZSM-5 additive is believed to retain activity for a longer time. ZSM-5 zeolite based catalysts in absence of
phosphate have tendency to get dealuminated under hydrothermal conditions.
Conventional silica-alumina binders used for binding Y type zeolites cannot be used for binding ZSM-5 zeolites, as they do not contain required phosphate for stabilizing these zeolites. Clay-phosphate based binders used for binding ZSM-5 zeolites cannot be used for binding Y zeolites having lower SiC"2 to AI2O3 ratio, due to severe dealumination which results in loss of catalytic activity.
While Y zeolite based FCC catalysts with conventional silica-alumina binder selectively crack heavy feed molecules into gasoline range molecules, ZSM-5 zeolite based catalysts
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bonded with clay phosphate binder selectively produce higher amount of C3 to C4 olefins by selective cracking of paraffins and alkyl aromatics present in the feed.
Differences in cracking pattern with two catalysts made with ZSM-5 and Y zeolite is attributed to the size and architecture of the pores present in these two zeolites. These two zeolites cannot be bonded with a common binder. Present practice of employing ZSM-5 zeolites for conventional FCC reaction is through making separate additive catalyst with a phosphate based binder and these catalysts are called as ZSM-5 additives. These additives are used in the range 1 to 6 wt % level of total catalyst present in inventory. Further increase in ZSM-5 additive catalyst in the inventory reduces the catalytic conversion, due to the dilution effect. This limitation in conversion on using additives in place of FCC catalysts, is due to the fact that, only medium pores in the range 5.4 to 5.5°A are present in ZSM-5 zeolites. These pores will not permit the entry of bulky hydrocarbon molecules for cracking. This limitation is known as "reactant selectivity" and is explained in an issue of "Zeolites" 4, 203 (1984). Further, distribution of ZSM-5 zeolite particles is restricted only on additive catalyst particles and hence effective use of this zeolite is limited.
Hence, there is a need to develop a process for a cracking catalyst, which can simultaneously bind both large pore Y zeolite with low SiC<2 to AI2O3 ratio and medium pore, high silica ZSM-5 zeolite. Formulation of single particle cracking catalyst with two types of zeolites will address the limitations encountered with the existing catalyst formulations.
OBJECTS OF THE INVENTION
The primary object of the present invention is to provide a stabilized dual zeolite catalyst
with a common silica alumina binder for binding high silica zeolite and low silica
» -■■■-.
molecular sieve.
Another object of the present invention is to provide a stabilized dual zeolite catalyst
having low coke formation for catalytic cracking process.
Yet another object of the present invention is to provide a stabilized dual zeolite catalyst.
having an enhanced hydrothermal stability.
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Still another object of the present invention is to provide a stabilized dual zeolite catalyst
with enhanced stability of Y zeolite.
Yet another object of the present invention is to provide a stabilized dual zeolite catalyst to
handle bulky hydrocarbon molecules present in the feed.
Still another object of the present invention is to develop a process for preparing a
stabilized dual zeolite catalyst composition suitable for catalytic cracking process.
Further object of the present invention is to develop a process for preparing cracking
catalyst for enhancing conversion and LPG selectivity.
Yet another object of the present invention is to develop a process for simultaneously
reduce bottom and enhance LPG.
Still another object of the present invention is to develop a process for preparing stabilized
high silica zeolite, which is suitable for incorporation to conventional silica alumina
binder.
Yet another object of the present invention is to develop a process for preparing pure
stabilized high silica zeolite, which is suitable for incorporation in to conventional silica
alumina binder.
It is another object of the present invention to develop a process for preparing pure
stabilized high silica zeolite, which is suitable for incorporation to conventional silica
alumina binder along with low soda rare earth exchanged Y zeolite.
It is further object of the present invention to develop a process for preparing a catalyst
composition by incorporating increased amount of stabilized high silica zeolite in to silica
alumina binder without diluting conversion efficiency of Y zeolite component.
Yet another object of the present invention is to develop a process for a cracking catalyst
having improved hydrothermal stability.
SUMMARY OF THE INVENTION
The present invention provides a stabilized dual zeolite low coke forming single particle
catalyst, bonded with silica alumina binder, suitable for cracking heavy residual hydrocarbon feeds and having enhanced hydrothermal stability and the process for binding high silica zeolite and low silica molecular sieve into a stabilized dual zeolite catalyst.
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DETAILED DESCRIPTION OF THE PRESENT INVENTION
Accordingly, the present invention provides for a stabilized dual zeolite low coke forming
single particle catalyst, bonded with silica alumina binder, suitable for cracking heavy residual hydrocarbon feeds and having enhanced hydrothermal stability, said catalyst comprising:
(a) stabilized "high silica zeoYrte in me range of \ wf/o to 5t> wfVo;
(b) low silica molecular sieve in the range of 1 wt% to 40 wt%;
(c) silica in the range of 1 wt% to 15 wt%;
(d) alumina in the range of 5 wt% to 30 wt%; and
(e) clay in the range of 10 wt% to 50wt%;
An embodiment of the present invention wherein the stabilized high silica zeolite consist of:
(a) a phosphate source in the range of 1 wt% to 40 wt%;
(b) high silica zeolite in the range of 5 wt% to 99 wt%; and
(c) clay in the range of 0 Wt% to 50 wt%.
Another embodiment of the present invention wherein the clay is selected from the group
consisting of kaolin and halloysite.
Yet another embodiment of the present invention wherein the high silica zeolite is selected
from the group consisting of ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38,
ZSM-48, ZSM-57, Zeolite beta, mordenite and preferably ZSM-5.
Still another embodiment of the present invention wherein the low silica molecular sieve is
selected from the group consisting of faujasite, mordenite, beta, MCM mesoporous zeolite
andL.
Yet another embodiment of the present invention wherein the low silica molecular sieve is
exchanged with NH3.
Still another embodiment of the present invention wherein the low silica molecular sieve is
exchanged with rare earth cations selected from the group consisting of lanthanum, cerium,
praseodymium, neodymium, samarium and gadolinium.

Yet another embodiment of the present invention wherein the low silica molecular sieve
having rare earth metal oxides in the range of 0.1 to 10 wt%.
Still another embodiment of the present invention wherein the phosphate source is selected
from the group consisting of phosphoric acid, ammonium di hydrogen phosphate,
ammonium mono hydrogen phosphate, tri-ammonium phosphate, ammonium
hypophosphate, ammonium ortho phosphate, ammonium di hydrogen ortho-phosphate,
ammonium mono hydrogen ortho-phosphate, ammonium hypo phosphite, ammonium di
nvdrogen ortho-phosphite or a mixture thereof.
Yet another embodiment of the present invention wherein the alumina is a pseudoboehmite
having a crystal size ranging from about 3 nm to 30 nm.
Still another embodiment of the present invention wherein the silica is in colloidal form of
particles having a mean diameter ranging from about 4 nm to 30 nm.
Yet another embodiment of the present invention wherein the stabilized high silica zeolite
has silica to alumina ratio from 10 to 300.
Still another embodiment of the present invention wherein the silica alumina binder is a
reaction product of acidified colloidal silica and acidified pseudoboehmite alumina.
Yet another embodiment of the present invention wherein the organic acid used for
acidifying colloidal silica is selected from the group consisting of nitric acid, hydrochloric
acid, formic acid and acetic acid.
Further embodiment of the present invention wherein the organic acid used for acidifying
pseudoboehmite alumina is selected from the group consisting of acetic acid, formic acid,
nitric acid and hydrochloric acid or a mixture thereof.
Still another embodiment of the present invention wherein said catalyst produces gasoline
having Research Octane Number (RON) 92-93.
Yet another embodiment of the present invention wherein the particle size of the catalyst is
the range of 20-150 microns.
Still another embodiment of the present invention wherein the particle size of the catalyst
is in the range of30-100 microns.
Yet another embodiment of the present invention wherein said catalyst having reduced
coke formation property in the range of 12.99 -12 wt%.
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An embodiment also provides a process for preparing hydrocarbon conversion, stabilized
dual zeolite catalyst, comprising essentially of stabilized high silica zeolite and a low silica molecular sieve, said process^omprising the steps of:
(a) loading high silica zeolite into a reactor and maintaining the zeolite at a temperature ranging between 100-125°C for about 30 minutes;
(b) heating the high silica zeolite to a temperature in the range of 450-500°C for about 90 minutes in nitrogen atmosphere;
(c) holding the zeolite at about 450-600°C for about 90 minutes in an atmosphere steam containing phosphate;
(d) cooling the zeolite to obtain stabilized high silica zeolite;
(e) treating an alumina with a dilute organic acid and gelling it for about 10 minutes to obtain alumina binder;
(f) adding demineralised water to the gel alumina to make the alumina binder free flowing;
(g) adding acidified ammonium polysilicate to the gel alumina; v * •?*'
(h) adding milled clay slurry to the product of st^h)^^ ^ '' ^
(i) adding milled slurry of low silica molecular sieve;
(j) adding demineralised water to obtain silica-alumina-clay and low silica molecular
sieve slurry; (k) adding the stabilized high silica zeolite as obtained in step (d) to the silica-alumina-clay-low silica molecular sieve slurry of step (j); and (1) spray-drying the slurry and calcining the same to obtain the stabilized dual zeolite catalyst. Still another embodiment of the present invention wherein the stabilization of high silica zeolite can be optionally performed in the following steps:
(a) preparing phosphate-clay slurry using a phosphate source and a clay with demineralised water;
(b) adding high silica zeolite to the slurry;
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(c) drying the product at a temperature in the range of 60-120°C in an oven; and
(d) pulverizing the product followed by calcination at about 400-600°C to obtain stabilized high silica zeolite;
Yet another embodiment of the present invention wherein the stabilized high silica zeolite
has silica to alumina ratio from 10 to 300.
Still another embodiment of the present invention wherein the high silica zeolite is selected
from the group consisting of ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38,
ZSM-48, ZSM-57, Zeolite beta, mordenite and preferably ZSM-5.
Yet another embodiment of the present invention wherein the stabilized high silica zeolite
contains optionally clay selected from the group consisting of kaolin and halipysite. ,
Still another embodiment of the present invention wherein the phosphate source is selected
from the group consisting of phosphoric acid, ammonium di hydrogen phosphate,
ammonium mono hydrogen phosphate, tri-ammonium phosphate, ammonium
hypophosphate, ammonium ortho phosphate, ammonium di hydrogen ortho-phosphate,
ammonium mono hydrogen ortho-phosphate, ammonium hypo phosphite, ammonium di
hydrogen ortho-phosphite or a mixture thereof.
Yet another embodiment of the present invention wherein the colloidal silica sol has a pH
between 7.0 and 11.5,_
Still another embodiment of the present invention wherein the colloidal silica consists of
silica particles having a mean diameter ranging from about 4 nm to 30 nm.
Yet another embodiment of the present invention wherein the colloidal silica contains soda
in the range of from 0.01 to 0.20 wt%.
Still another embodiment of the present invention wherein said silica sol is acidified to a
pH between 0.5 and 3.5 before use.
Yet another embodiment of the present invention wherein said silica sol is acidified using
a acid selected from group consisting of nitric acid, hydrochloric acid, formic acid and
acetic acid.
Still another embodiment of the present invention wherein said alumina is a
pseudoboehmite.
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Yet another embodiment of the present invention wherein said alumina has crystallite size
?-"--*—■' ~.
ranging from about 3 nm to about 30 nm.
Still another embodiment of the present invention wherein said alumina has soda content
ranging between 0.001 and 0.1 wt%.
Yet another embodiment of the present invention wherein the alumina used is acidified
using acids selected from the group consisting of acetic acid,formic acid, nitric acid and
hydrochloric acidor a mixture thereof.
Still another embodiment of the present invention wherein ratio of high silica zeolite to
low silica molecular sieve is in the range of 1-50:1-40. (1:40 to 50:1).
The present invention is further explained in the form of following preferred embodiments.
Clays
Clays are commonly used as major component of cracking catalysts. They are favored due
to their low cost and used as diluent and density modifier. Clays are used in finely divided form with a size below 3 microns. The most common varieties of clays used in cracking catalyst formulations are kaolinite and halloysite. Clays have a two-layer structure, consisting of alternating sheets of silica in tetrahedral configuration and alumina in octahedral configuration. These sheets are separated with a gap of 7.13 °A. Dry atmosphere equilibrated clay has moisture content of about 15 wt%. Clays are good sources for silica and alumina as they contain about 45 wt % of silica-and.38 wt% of alumina.
Synthetic faujasite
Synthetic faujasite also referred to, as Y zeolites are the most commonly used crystalline
inorganic aluminosilicates, having pores in the range 6.5 to 13.5°A in its framework. These
zeolites are synthesized with SiCh to AI2O3 ratio in the range 4.5 to 6 and 12-13-wt
%Na20. To make them suitable for catalytic application, soda present inside for balancing
electrovalence is required to be exchanged with a proton, via ammonium exchange
followed by calcination. Higher silica to alumina ratio zeolite may be further prepared by
modification of synthetic forms by steaming, chemical treatment or replacement of
framework aluminum with silica. These modification steps for ultrstabilization of Y zeolite
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drastically reduce the catalytic activity of the zeolite. Rare earth loaded faujasite zeolite exhibit superior hydrothermal stability without requiring enhancing silica alumina ratio of framework. Rare earth may be one of or the mixture of rare earth oxides lanthanum, cerium, praseodymium, neodymium, samarium and gadolinium. Total rare earth oxide content in the zeolite may vary from 0.1 wt% to 10 wt%.
Stabilized ZSM-5 zeolite
ZSM-5 zeolites are medium pore, high silica crystalline inorganic material having pores in
the range 5.4 to 5.5°A. This zeolite is known for dewaxing and isomerization abilities of hydrocarbons. In cracking processes, these zeolites lead to production of higher LPG and high-octane gasoline. ZSM-5 zeolites with conventional silica alumina binders cannot sustain LPG selectivity due to the requirement of stabilization of acid sites and pores with phosphate radicals. The present invention shows how to stabilize ZSM-5 zeolite using phosphate compounds, so that these can be incorporated into conventional silica-alumina based binders along with rare earth exchanged Y zeolite. Step of zeolite modification involves reacting the required amount of phosphates with clay and ZSM-5 zeolite, drying, pulverizing and calcination of the product. Zeolite stabilization may be carried out with a novel procedure of steaming in presence of phosphate source. The phosphate source could be phosphoric acid, ammonium di hydrogen phosphate, ammonium mono hydrogen phosphate, tri-ammonium phosphate, ammonium hypophosphate, ammonium ortho phosphate, ammonium di hydrogen ortho-phosphate, ammonium mono hydrogen ortho-phosphate, ammonium hypophosphite, ammonium di hydrogen ortho-phosphite, and mixture thereof. ^Stabilization of ZSM-5 zeolite with clay and phosphate results in_a product with unchanged or partially increased surface area and crystallinity for ZSM-5
zeolite. Increase in surface area and crystallinity may be attributed to the extension of the
""' '"■ "^~»_„.
zeolite to crystalline alumina phosphate having structure analogous to ZSM-5. ZSM-5
zeolites with silica alumina molar ratio varying from 10 to 300 may be considered for
preparing stabilized zeolite.
Colloidal silica
t3

Colloidal silica is aqueous colloidal dispersions of silica particles, stabilized by the use of small quantities of soda or ammonium. These products having soda less than 0.2 wt % and can be readily used for matrix or catalyst binding purpose. These are stable between pH of 8.5 and 11. These products are commercially available in varying particle size ranging from 7 to 22 nm. Alumina
Pseudoboehmite alumina with soda, less than 0.1 wt % are ideal binders for different zeolite based catalysts as they can be converted to a glue by reacting with acids like nitric acid, formic acid or acetic acid. Glue alumina can be mixed with molecular sieve, clay and colloidal silica and spray dried. Once spray dried product is calcined, alumina gets transformed into gamma phase, a hard material, which holds clay, zeolite and other catalyst ingredients together to form attrition resistant mass. Varieties of pseudoboehmite alumina are commercially available in different crystallite sizes and surface area.
Cracking catalyst
In a preferred method for preparing cracking catalyst of present invention, (a) a stabilized
high silica zeolite is prepared by reacting a phosphate compound with pure high silica zeolite or with a mixture of clay and high silica zeolite at higher temperature preferably under steaming conditions, (b) preparing silica alumina binder by reacting acidified colloidal silica using preferably an organic acid with a glue alumina prepared by geling pseudoboehmite alumina with an organic acid, (c) adding finely ground paste of kaolin clay to silica alumina binder under vigorous stirring, (d) followed by addition of a finely ground slurry of low silica zeolite under stirring, (e) further, followed by addition of finely ground slurry of stabilized high silica zeolite to obtain a slurry ready for spray drying having composition, 1 to 50 wt% stabilized high silica zeolite, 5 to 30 wt % alumina binder, 1 to 15 wt% silica, 10 to 50 wt% kaolin clay and 1 to 40 wt% low silica molecular sieve, (f) drying the slurry and (g) calcination.
The present invention is further explained in the form of following examples. However, these examples should not be construed as limiting the scope of the invention.
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EXAMPLE 1
Preparation of stabilized higB silica zeolite
50 gm of diammonium hydrogen phosphate is dissolved in 250 gm demineralised water.
To this phosphate solution, 205-3 gm of kaolin clay (having 15 wt % moisture content) is added under vigorous stirring- To the clay-phosphate slurry, a fine paste of zeolite prepared by grinding 64.52 grn of ZSM-5 zeolite (having SiC^/A^Os ratio of 30 and moisture content 7 wt %) with 65 gm de-mineralized water, is added under vigorous stirring. Final slurry with solid content of 42 wt % and having pH of 7.5 is oven dried, pulverized and calcined to 5O0°C. The stabilized zeolite thus obtained having a surface area of 86 m2/gm and ZSM-5 content of 24 % (as determined by X-ray diffraction) is considered for the preparation of stabilized dual zeolite catalyst.
EXAMPLE 2 Preparation of stabilized pure high silica zeolite.
100 gm of hydrogen form of ZSM-5 zeolite, is loaded into a steam reactor and heated to
125°C for about 30 minutes, while the zeolite is purged with nitrogen gas. After holding the zeolite for 30 minutes, it is further heated to 500°C for another 90 minutes. When the temperature of the zeolite readies 500°C, the zeolite is maintained at that temperature for 90 minutes, while a 50 gm solution having dissolved diammonium hydrogen phosphate (6 gm in 44gm de-mineralized water), is injected into the hot zeolite. At the end zeolite is allowed to cool. This procedure gives stabilized ZSM-5 zeolite, which can be easily incorporated into FCC catalyst formulation along with low soda faujasite zeolite. The phosphate stabilized ZSM-5 having a surface area of 330 m2/gm andJC-ray crystallinityjof 92% is considered for the preparation of stabilized dual zeolite catalyst. •
EXAMPLE 3
Preparation of cracking catalyst using stabilized high silica zeolite as prepared under Example 1.
10.5 gm of formic acid is diluted in 196 gm de-mineralized water. To this acid 69.08 gm
of Pural SB grade alumina (having moisture content 24.0 wt%) is added under stirring. This acidified alumina slurry is allowed to gel for 10 minutes and after words made free flowing by adding 100 gm of de-mineralized water. 18.75 gm of ammonium polysilicate
\5

(SIO2, 40 wt%) is acidified with 2 gm of formic acid (85 wt%) diluted in 10 gm de-mineralized water and added to the gel alumina under stirring. To the silica alumina slurry 270 gm of milled kaolin clay slurry (solid content 50 wt%) is added under stirring. For making the slurry free flowing 100 gm of additional de-mineralized water is used. 40.32 gm of REY zeolite (4 wt% Re203,1 wt% Na20 and 7 wt % moisture) is ground in to a fine paste with equivalent weight of de-mineralized water and this is added to silica-alumina-clay slurry. Finally, 67.5 gm of stabilized high silica zeolite prepared as per example 1, is added to the silica-alumina-clay-REY zeolite slurry under stirring. At the end a slurry having pH 2.9 is spray dried. Dried micro spheres are calcined at 500°C for one hour. Catalyst fraction between 20 micron and 120 micron is steamed at °C for 3 hours under 100 wt% steam for equilibrating the catalyst.
Thus steamed catalyst is evaluated using a mix feed consisting 80wt% RCO and 20wt% coker gasoline (feed properties are shown in Tables 1 and 2) with a catalyst to oil ratio of 3. Under this condition catalyst produced products as shown in Table 3.
TABLE 1
Physico-chemical properties of mix feed.

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EXAMPLE 4
This example describes a procedure for the preparation of cracking catalyst employing stabilized pure zeolite as obtained in Example 2
10.5gm of formic acid is diluted in 196 gm de-mineralized water. To this acid 69.08 gm of Pural SB grade alumina (moisture content 24.0wt%) is added under stirring. This acidified
17

alumina slurry is allowed to gel for 10 minutes. This gel is made free flowing by adding 100 gm of de-mineralized water. 18.75 gm of ammonium polysilicate (Si02, 40%) is acidified with 2 gm of formic acid (85 wt%) diluted in 10 gm de-mineralized water and added to the gel alumina under stirring.
To the silica alumina slurry, 375 gm of fine, milled clay slurry (50wt% solid content) is added under stirring. For making the slurry free flowing 100 gm of additional de-mineralized water is added under stirring. 40.32 gm of REY zeolite (4 wt% Re203, 1 wt% Na20 and 7 wt% moisture) is ground in to a fine paste with equivalent weight of de-mineralized water and this is added to silica-alumina-clay slurry. Finally, a slurry of stabilized pure high silica zeolite (stabilized zeolite from Example 2), prepared by milling 15 gm of zeolite with 20 gm of de-mineralized water is added to the slurry of silica-alumina-clay-REY zeolite, under stirring. At the end slurry with pH 2.8 is spray dried. Dried micro spheres are processed similar to that of Example 3. Results of characterization and performance are shown in Table-3.
TABLE 3

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EXAMPLE 5 This example shows inadequate stability of a catalyst prepared by employing a binder disclosed under example 17 of U.S Patent No.5,190,902.
A cracking catalyst is prepared having composition, clay 80.3 wt%, REY zeolite 12.08 wt% and PO4 7.6 wt%, taken from phosphoric acid 85 wt% as source. Spray dried micro spheres are calcined, steam deactivated and characterized for surface area and X-ray crystallinity, results of this study are shown in Table.4.
TABLE 4

ADVANTAGES:
1. The dual zeolite catalyst of the present invention uses conventional silica alumina binder as a common binder for binding high silica zeolite and low silica molecular sieve.
2. The dual zeolite catalyst composition of the present invention, produce lower coke.
3. The dual zeolite catalyst of the present invention is effective towards conversion and increasing LPG yields.
19

We Claim;
1. A process for preparing stabilized dual zeolite single particle catalyst, said catalyst
comprising a stabilized high silica zeolite and a low silica molecular sieve, said
process comprising the steps of:
(a) preparing stabilized high silica zeolite;
(b) treating an alumina with a dilute acid and gelling it for about 10 minutes to obtain an alumina binder;
(c) adding demineralised water to the alumina binder to make the alumina binder free flowing;
(d) adding an acidified ammonium polysilicate to the alumina binder;
(e) adding milled clay slurry to the product of step (d);
(f) adding milled slurry of low silica molecular sieve to the product of step (e);
(g) adding demineralised water to the product of step (f) to obtain a silica-jalumina-clay-low silica molecular sieve slurry;
(h) adding the stabilized high silica zeolite as obtained in step (a) to the silica-alumina-clay-low silica molecular sieve slurry of step (g); and
(i) spray-drying the slurry of step (h) and calcining the resulting product to obtain the stabilized dual zeolite catalyst
2. A process as claimed in claim 1 wherein in step (a), the stabilized high silica zeolite
is obtained by:
(a) loading high silica zeolite into a reactor and maintaining the zeolite at a temperature ranging between 100-125°C for about 30 minutes;
(b) heating the high silica zeolite to a temperature in the range of 450-500°C for about 90 minutes in nitrogen atmosphere;
(c) holding the zeolite at about 450-600°C for about 90 minutes in an atmosphere of steam containing phosphate, and
(d) cooling the zeolite to obtain stabilized high silica zeolite
3. A process as claimed in claim 1 wherein in step (a), the stabilized high silica zeolite
is obtained by:
(a) preparing phosphate-clay slurry using a phosphate source and a clay with demineralised water;

(b) adding high silica zeolite to the slurry;
(c) drying the product at a temperature in the range of 60-120°C in an oven, and
(d) pulverizing the product followed by calcination at about 400-600°C to obtain stabilized high silica zeolite;

4. A process as claimed in claim 1, wherein the stabilized high silica zeolite has silica to alumina ratio from 10 to 300.
5. A process as claimed in claim 1, wherein the high silica zeolite is selected from the group consisting of ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, ZSM-48, ZSM-57, Zeolite beta, mordenite and preferably ZSM-5.
6. A process as claimed in claim 1, wherein the stabilized high silica zeolite contains optionally clay selected from the group consisting of kaolin and halloysite.
7. A process as claimed in claim 3, wherein the phosphate source is selected from the group consisting of phosphoric acid, ammonium di hydrogen phosphate, ammonium mono hydrogen phosphate, tri-ammonium phosphate, ammonium hypophosphate, ammonium ortho phosphate, ammonium di hydrogen ortho-phosphate, ammonium mono hydrogen ortho-phosphate, ammonium hypo phosphite, ammonium di hydrogen ortho-phosphite or a mixture thereof.
8. A process as claimed in claim 1, wherein the colloidal silica sol has a pH between 7.0 and 11.5.
9. "A process as claimed in claim 1, wherein the colloidal silica consists of silica particles having a mean diameter ranging from about 4 nm to 30 nm.
10. A process as claimed in claim 1, wherein the colloidal silica contains soda in the range of from 0.01 to 0.20 wt%.
11. A process as claimed in claim 1, wherein said silica sol is acidified to a pH between 0.5 and 3.5 before use.
12. A process as claimed in claim 1, wherein said silica sol is acidified using a acid selected from group consisting of nitric acid, hydrochloric acid, formic acid and acetic acid.
13. A process as claimed in claim 1, wherein said alumina is a pseudoboehmite.
14. A process as claimed in claim 1, wherein said alumina has crystallite size ranging from about 3 nm to about 30 nm.

15. A process as claimed in claim 1, wherein said alumina has soda content ranging between 0.001 and 0.1 wt %.
16. A process as claimed in claim 1, wherein step (b), the alumina used is acidified using acids selected from the group consisting of acetic acid, formic acid, nitric acid and hydrochloric acid or a mixture thereof.
17. A process as claimed in claim 1, wherein ratio of high silica zeolite to low silica molecular sieve is in the range of 1-50: 1-40.
18. A process for preparing stabilized dual zeolite single particle catalyst substantially as herein described and illustrated.


Dated this 13th day of February, 2001

Omana Ramakrishnan
Of K & S Partners
Agent for the Applicants.