Production of fluid catalytic cracking catalysts

Preparation of fluid catalytic cracking catalysts is improved by incorporating a viscosity-reducing agent, having the general formula of Al.sub.2 (OH).sub.5 NO.sub.3, in the aqueous slurry containing the catalyst components of zeolite, clay, aluminous binder, and a silica source, prior to drying of the slurry. The viscosity-reducing additive allows an increase in the solids content of the aqueous slurry and thus improves the efficiency of the drying operation.

BACKGROUND OF THE INVENTION 
This invention relates to the production of fluid catalytic cracking 
catalysts. These fluid catalytic cracking catalysts (hereinafter "FCC 
catalysts") are generally prepared from a mixture of zeolite particles, 
clay, an alumina-containing binder, and a silica source. These 
constituents are admixed in an aqueous slurry in certain proportions, then 
the aqueous slurry is subjected to drying to form the essentially 
water-free FCC catalyst particles. 
The productivity of the process is generally limited by the solids content 
of the aqueous slurry subjected to the drying step. The higher the solids 
content of the slurry, the better the throughput rate in a given piece of 
equipment with simultaneous better utilization of the heat input in the 
dryer. When the drying operation is accomplished by using conventionally 
available drying equipment, such as spray-driers, the viscosity of the 
aqueous slurry plays a significant role. Spray driers are usually equipped 
with nozzles or rotating discs and if the slurry has a high viscosity, 
which is related to the solids content of the slurry, plugging of the 
nozzles or stoppage of the discs will occur interrupting the production of 
the FCC catalysts. Consequently, a balance must be found between the 
desired production rate and the solids content of the aqueous slurry. 
In our copending application Ser. No. 420,439, filed Sept. 20, 1982 now 
U.S. Pat. No. 4,443,553, a process for reducing the viscosity of aqueous 
slurries containing the FCC catalyst forming constituents, is described. 
The reduction in viscosity and corresponding improvement in the production 
rate is achieved by the incorporation of an additive having the general 
formula of (Al.sub.2 (OH).sub.6-y Cl.sub.y).sub.x where x=1 to 6 and y=1 
to 2. This additive is incorporated in the aqueous slurry in an amount 
equivalent to from about 0.5 to about 2.5% by weight calculated as 
Al.sub.2 O.sub.3 and based on the solids content of the slurry. The 
addition of this additive to the slurry allows a significant increase in 
the solids content of the slurry, for example, up to about 20% by weight. 
Although the addition of the (Al.sub.2 (OH).sub.6-y Cl.sub.y).sub.x 
additive provides significantly improved production efficiency and energy 
savings, the FCC catalyst particles produced will contain a small quantity 
of chloride residue. Although in most catalytic cracking applications, the 
residual chloride content (0.1-0.3% by wt.) of the FCC catalyst does not 
create problems, there are a few processes where the presence of the 
chloride could interfere with the efficiency of the catalytic cracking. 
Consequently, there has arisen a need to find an additive which on the one 
hand reduces the viscosity of the aqueous slurry and on the other hand 
does not leave behind an anionic impurity which could interfere with any 
FCC operation. It has been surprisingly discovered that there is an 
alumina-containing additive, having the general formula of Al.sub.2 
(OH).sub.5 NO.sub.3, which accomplished the desired viscosity reduction, 
but when incorporated in the aqueous slurry used for the FCC catalyst 
preparation, will not provide any residual effect in terms of catalyst 
performance and/or activity. 
BRIEF SUMMARY OF THE INVENTION 
In the process of producing fluid catalytic cracking catalysts by preparing 
an aqueous slurry from the components forming the catalyst, such as 
zeolite, clay, alumina-containing binder, and a silica source, and then 
subjecting the slurry to drying to form the catalyst particles, the 
efficiency of the drying step can be significantly improved by 
incorporating in the aqueous slurry a viscosity-reducing additive. The 
viscosity-reducing additive has the general formula of Al.sub.2 (OH).sub.5 
NO.sub.3 and is incorporated in the slurry in an amount sufficient to 
reduce the viscosity of the slurry, generally in a quantity equivalent to 
about 0.2% to about 2.5% by weight, calculated as Al.sub.2 O.sub.3 and 
based on the total solids content of the aqueous slurry. The 
viscosity-reducing additive, when incorporated in the slurry in the 
amounts indicated, can significantly reduce the slurry viscosity. This 
allows an increase in the solids content of the slurry to be dried with 
corresponding increase in production rate and drier efficiency.

DETAILED DESCRIPTION OF THE INVENTION 
This invention relates to an improved process for producing FCC catalysts. 
More particularly, the present invention concerns an improvement in the 
preparation of FCC catalysts wherein an aqueous slurry of catalyst 
components is dried to form the catalyst particles. The improvement in the 
production of FCC catalysts is accomplished by incorporating in the 
aqueous slurry a viscosity-reducing additive which will allow an increase 
in the solids content of the slurry resulting in increased productivity 
and improved energy balance. 
Preparation of FCC catalysts is a well-known manufacturing operation and is 
generally accomplished by preparing an aqueous slurry of the catalyst 
forming constituents. The catalyst-forming constituents usually employed 
in the production of FCC catalysts are zeolite particles, clay, an 
alumina-containing binder, and a silica source. 
The zeolite component utilized in the preparation of the FCC catalyst, 
according to the present process, is generally selected from faujasite 
zeolites of the Y-type. In the preparation of Y-type zeolites from alumina 
and sodium silicate, the formed product often contains a relatively high 
percentage of alkali metal ions. This is considered detrimental for many 
applications and consequently, the zeolite is subjected to ion exchange to 
replace to a large extent the alkali metal ions with more desirable ions, 
such as ammonium, hydrogen, alkaline earth, and rare earth metal cations. 
For the instant process, such zeolites are preferred which contain rare 
earth metal ions as replacement for the alkali metal ions. The quantity of 
zeolites incorporated in the FCC catalyst is generally in the range from 
about 10 to about 35% by weight; consequently, the aqueous slurry used for 
making the FCC catalyst also contains this quantity of zeolite dispersed 
in the aqueous medium. 
The alumina-containing binder used for the preparation of the FCC catalyst 
can be selected from aluminas having either an alpha alumina monohydrate 
or a pseudoboehmitic structure. The alpha alumina monohydrate is generally 
derived from the water hydrolysis of aluminum alkoxides, is commercially 
available as "CATA", and is characterized by a surface area in excess 
of about 200 m.sup.2 /g, an Al.sub.2 O.sub.3 content of at least about 70% 
by weight. The pseudoboehmite alumina is also available commercially as 
"Kaiser SA" and is characterized by an x-ray diffraction pattern wherein a 
broad peak appears in the range of 10-18 Angstroms peaking at 13.5 
Angstroms when Cu K.alpha. radiation is employed. It is further 
characterized by an Al.sub.2 O.sub.3 content of at least 70% by weight and 
a surface area in excess of about 200 m.sup.2 /g. The quantity of binder 
incorporated in the aqueous slurry is usually in the range from about 7 to 
about 21% by weight, calculated as Al.sub.2 O.sub.3 and based on the total 
solids content of the aqueous slurry. For optimum results, the 
alumina-containing binder is peptized with an acid, such as formic acid, 
prior to its incorporation in the aqueous slurry. Peptization can be 
readily accomplished in accordance with the teachings of U.S. Pat. No. 
4,086,187, the teachings of which are incorporated herein by reference. 
The clay component used for making the FCC catalyst can be selected from 
conventionally employed clays, such as kaolinite and crystalline kaolin. 
Suitable kaolins include ball clay and halloysite. The clay component is 
incorporated in the aqueous slurry in amounts in the range of about 60 to 
70% by weight based on the total solids content of the aqueous slurry, the 
clay quantity being calculated on the dry weight of the clay when dried at 
about 930.degree. C. (1700.degree. F.) for about 1 hour. 
Suitable silica source for the FCC catalyst is a polysilicate, such as 
described in detail in the aforementioned U.S. Pat. No. 4,086,187. The 
quantity of silica added to the slurry is generally kept within the range 
from about 1 to about 7% by weight based on the total solids content of 
the slurry. 
The aforementioned components are incorporated in the aqueous slurry and 
the slurry is then agitated to assure uniform mixing and dispersion of the 
constituents. Subsequent to the incorporation of these ingredients in the 
slurry, the viscosity-reducing additive is added to the slurry under 
agitation. The quantity of Al.sub.2 (OH).sub.5 NO.sub.3 additive added to 
the slurry is kept within the range from about 0.2 to about 2.5% by weight 
(calculated as Al.sub.2 O.sub.3) based on the total solids content of the 
aqueous slurry. Best viscosity-reducing results are achieved when the 
additive is employed in the range from about 0.5 to about 2.0% by weight. 
The quantity to be incorporated in the aqueous slurry within the ranges 
indicated depends on the final solids content of the slurry and viscosity 
desired. Thus, the higher the desired final solids content of the slurry, 
the higher the quantity of additive incorporated. Addition of the 
viscosity-reducing additive to the slurry causes reduction in the slurry 
viscosity within a short time period, usually within minutes. This 
reduction in viscosity allows the addition of additional FCC catalyst 
components to the slurry in the same ratio as added to the original 
slurry. It has been found that in the absence of the viscosity-reducing 
additive, the maximum solids content of the slurry is limited to about 
20-25% by weight. Addition of the Al.sub.2 (OH).sub.5 NO.sub.3 agent 
allows the slurry solids content to be increased to about 30% by weight 
without increasing the viscosity of the slurry of increased solids content 
beyond the viscosity obtained without the additive. This significant 
increase achieved in solids content without deleterious viscosity effects 
represents a significant advance in the art of manufacturing FCC catalyst 
from both a productivity and an energy utilization point of view. 
The following examples will further present the novel aspects of the 
present process. 
EXAMPLE I 
Five aqueous slurries were prepared for the manufacture of FCC catalyst. 
Each slurry had a total solids content of 25% by weight and each contained 
a blend of Y-type, rare earth metal exchanged zeolite 18%, alpha alumina 
monohydrate binder 18%, kaolin-type clay 61.5% and ammonium polysilicate 
2.5% (all percentages are weight percents based on the total solids 
content). Each of the slurries was prepared by first peptizing the alumina 
binder with aqueous formic acid under agitation followed by addition of 
the clay component to the slurry of peptized alumina binder. The slurry 
was vigorously agitated for about 10 minutes followed by addition of the 
zeolite component under agitation. Finally, the ammonium polysilicate was 
incorporated in the slurry. Subsequently, varying quantities (0.2%, 0.4%, 
0.6%, 0.8%, and 1.0% by weight) of Al.sub.2 (OH).sub.5 NO.sub.3, 
calculated as Al.sub.2 O.sub.3 and based on the total solids content of 
the slurry, were added to the individual slurries to establish the 
viscosity-reducing effect of the additive. The viscosity measurements were 
tabulated and are provided in Table I and are also graphically shown in 
FIG. 1. 
TABLE I 
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Effect of Al.sub.2 (OH).sub.5 NO.sub.3 Additive Quantity 
on FCC Slurry Viscosity 
Al.sub.2 (OH).sub.5 NO.sub.3 % 
(Al.sub.2 O.sub.3 basis) 
0.20 0.4 0.6 0.8 1.0 
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Viscosity in cps prior 
23050 22500 22350 26400 24200 
to addn. of 
Al.sub.2 (OH).sub.5 NO.sub.3 
Viscosity in cps after 
21750 17600 8400 6650 5500 
addn. of 
Al.sub.2 (OH).sub.5 NO.sub.3 
______________________________________ 
From Table I, it can be readily observed that significant viscosity 
reductions can be achieved by incorporation of the Al.sub.2 (OH).sub.5 
NO.sub.3 additive. 
Example II 
In this Example, the residual anion content of FCC catalysts made with the 
instant Al.sub.2 (OH).sub.5 NO.sub.3 additive and with (Al.sub.2 
(OH).sub.6-y Cl.sub.y).sub.x additive were compared as a function of heat 
treatment temperature in a muffle furnace between the temperature range 
from about 93.degree. C. (200.degree. F.) and about 538.degree. C. 
(1000.degree. F.). The residual anion content (NO.sup.-.sub.3 or Cl.sup.-) 
was measured after the catalyst was subjected to heat treatment at five 
different temperatures within the range given. The results are tabulated 
in Table II and are also shown graphically in FIG. 2. 
TABLE II 
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Residual Anion Content of FCC Catalyst 
Made with Al.sub.2 (OH).sub.5 NO.sub.3 and (Al.sub.2 (OH).sub.6--y 
Cl.sub.y).sub.x 
Additives After Heat Treatment at Various Temperatures 
Heat Treatment 
Temp. in .degree.C. 
for 1 hour 93.degree. C. 
204.degree. C. 
315.degree. C. 
426.degree. C. 
537.degree. C. 
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Residual NO.sup.-.sub.3 
1.4 1.1 0.4 0.01 &lt;0.01 
Content in % of 
FCC Catalyst 
Residual Cl.sup.- 
1.6 1.5 0.8 0.4 0.1 
Content in % of 
FCC Catalyst 
______________________________________ 
It was further observed that during spray-drying of the aqueous slurry 
containing the Al.sub.2 (OH).sub.5 NO.sub.3 viscosity-reducing additive, 
no environmentally harmful NO.sub.x emissions occurred, which further 
enhances the significance of the instant process. 
Also, the incorporation of the additive in the FCC catalyst does not 
interfere with the catalyst activity or its physical properties, such as 
strength.