Note: Descriptions are shown in the official language in which they were submitted.
37~4
The present invention relates to the preparation of
hydrocarbon conversion catalysts, and more speciically to an
improved method for preparing zeolite containing catalysts
wherein crystalline aluminosilicate zeolite is dispersed in an
inorganic oxide matrix.
For many years zeolite containing hydrocarbon conver-
sion catalysts have been prepared by admixing an essentially
fully crystalline aluminosilicate such as faujasite with amorphous
inorganic oxides such as silica, silica-alumina, and alumina
hydrogels. Typical prior art processes involve irst forming a
batch of crystalline alumino silicate zeolite hy the hydrothermal
reaction of silica, alumina, sodium hydroxide and water. Sub-
sequent to obtaining the crystalline zeolite batch, the zeolite
is recovered from its reaction medium (mother liquor) and com- -
~bined with an amorphous gel component such as silica-alumina or
silica-alumina hydrogel. The gelled zeolite-amorphous hydrogel
composite is then washed to remove excess alkali metal salts,
ion exchanged with polyvalent metal ions, and dried.
It has been found that the batchwise preparation of
zeolite followed by incorporation in an amorphous gel matrix
::. . .. .
is a relatively expensive procedure from the standpoint of
materials in that the excess sodium silicate solu~ion which
results from the batchwise preparation of zeolite is normally ~
discarded. Furthermore, it is found that batch preparation of ~ -
zeolite on a commercial scale, wherein literally tons of
:
zeolite are formed, frequently leads to the preparation of ~
: .
~ products of varying quality.
;. : ,
Attempts to prepare zeolite catalysts on a commercial - -
scale using essentially continuous processes have not been
~ practlcal, primarily due to the fact preparation of fully
crystalline zeolite requires reaction periods substantially
longer than the subsequent catalyst forming operation.
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It is therefore an object of the present in~ention
to provide an improved method for prepariny zeolite containiny
catalysts.
It is another object to provide a method by which con-
ventional quantities of zeolite containing catalysts may be
prepared on an essentially continuous basis.
It is a further object to provide a zeolite hydro-
carbon conversion catalyst preparation method by which sub-
stantially full utilization of raw materials may be effectively
obtained.
These and still further objects o~ the present invention
will become readily apparent to one skilled in the art from
the following detailed description and specific examples.
Broadly, our invention comprises a procedure wherein
a crystalline aluminosilicate zeolite procursor reaction mixture
containing zeolite seed particles, i.e., nucleation centers,
which are effective for initiating the rapid crystallization of
zeolite, is reacted to form partially crystalline zeolite product,
and subsequently the partially crystalline reaction mixture is
diluted with water, and combined with gel forming components
such as mineral acid, carbon dioxide and/or acid aluminum salts.
More specifically, we have found that commercial
quantities of crystalline zeolite containing catalysts may be
quickly and economically prepared by the following procedures
: :
outlined belo~: -
1. A zeolite precursor reaction mixture which contains
alumina, silica, sodium hydroxide and water is admixed with
amorphous si1ica-alumina seed particles, i.e., nucleation
; centers, which possess a particle size of below about 0.1
micron.
2. The precursor reaction mixture is reacted at a
temperature of from about 90C. to reflux to obtain about
- 3 -
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15 to 100% crystallization of zeolite which is theoretically
obtainable from the reactants present.
3. The partially crystallized zeolite reaction mixture
is then diluted with sufficient water to dilute the excess
sodium silicate present to a level of about 7 to 3~ by weight
SiO2 basis. This Pilution also serves to quench the crystal-
lization reaction by lowering the reaction ternperature to
below about 50C.
4. The diluted reaction mixture is then admixed with
an acidic component such as mineral acids, (H2SO4HCl or NHO3),
carbon dioxide and/or acid aluminum salts such as alum to
gel the sodium silicate and thereby form an amorphous hydrogel
matrix. At this pOiIIt additional aluminum containing compounds
such as sodium aluminate or other catalyst components such
as clay may be added to the reaction mixture to impart the
desired concentration of amorphous alumina and/or clay to
the catalyst composition.
5. The gelled composition is then formed into desired
particles such as by spray drying, washed to remove soluble
salts such as sodium or sul~ate ion, and dried to remove excess
;
moistu~e. Optionally, the composition may b~ ion exchanged with~ -
stabilizing and/or catalytic promotor metal ions to enhance the
stability and/or catalytic properties of the catalyst composition.
In a particularly preferred embodiment of the present ,
inven*ion the above outlined process is conducted on a con- ~-
tinuous basis. Thus, for example, the zeolite crystallization
.,,~
process which requires only a few minutes due to the presence -~
.~ - ., ~.
of highly active crystallization initiation seed particles, may
be continuously performed in an elongated pipe type reactor. ~ -
The reactor is maintained at a temperature of from about 95 to -
., .
110C. at which crystallization of the faujasite rapidly takes
'' "' ' ' '
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~3~14
place. At the point in the reactor wherein khe desired deyree
of crystallization has occurred, normally from about 15 to 100%
crystallization of theory, cold water is admitted to the reactor
to lower the temperature of the reaction mixture to temperature
of from about ~0 to 50C. This quenching water is added in
amounts to achieve dilution of the excess silicate present in
the faujasite reaction mixture to a level of from about 7
to 3% based on the weight of silicate present. I'he diluted
zeolite reaction mixture is then admitted to a second elonyated
reactor to which an acidic yelling component is continuously
added. The gel reaction mass is then washed to remove excess
alkali metal and other soluble salts, spray dried, ion exchanged
and finally dried using conventional spray drying or other
catalyst forming procedures.
~s indicated above, the zeolite precursor reaction
mixture contains silica, alumina, water and alkali metal hydroxide. -~
In general the composition of the precursor reaction mixture '-~
will depend upon the precise type zeolite which is to be pro~
duced. For example, when it is desired to produce type X or Y
zeolite having a silica alumina ratio on the order of 2.5 to 6
the following ratios of ingredients may he utilized:
Ingredient Moles
SiO2 2.5 to 16 ~
A123 1 to 1 -
H2O 80 to 170
Na2O 3.0 7
On the other hand, when it is desired -to prepare type
~: zeolite, the following reaction ratio~s may be utilized: -
''
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- 5 -
~7(~4
Ingredient Moles
SiO2 1.5 to 2
A123 1 to 1
H2O 60 to 120
Na2O1.0 to 1.8
The silicate may be derived from any convenient
source such as sodium silicate or particulate colloidal silicaS
which are readily available for many commercial sources. The
alumina component is provided from any convenient source such
as sodi um aluminate or other soluble aluminum salt such as
aluminum sulfate, Al(NO3)3, AlC13.
The precursor reaction mixtures described in the
above are combined with zeolite seed particles or nucleation
centers which are capable of initiating the rapid crystalli~
zation of the crystalline aluminosilicate zeolite. Preferably -~
these seeds, i.e., nucleation centers, are silica-alumina ;
particles which are amorphous and which possess a particle size
of below about 0.1 micron and a SiO2 to A12O3 ratio of 5 to 1. ~-~
The zeolite seeds are prepared in the form of an aqueous slurry
by reacting the following ratio of ingredients:
Ingredient Moles ;
SiO2/A12O3 14 to 16
, :.,:-
Na2O/~12O3 15 to 17
H2O/Na2O 19 to 21
The seed preparation mixture is reacted at a temperature
, ,
of from about 15 to 20C. and allowed to stand 16-24 hours
at room temperature. The resultant slurry which remains stable ~ ~-
for a period o~ many weeks is then utilized to initiate the
crystallization of zeolite from the precursor reaction mixture.
It is generally found that the seed slurry described ~ --
above is added to the precursor reaction mixture in amounts
ranging from about 5 to 20 parts by weight of the seed slurry
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1037~4
per part by weight o~ the A12O3 present in the zeolite pre-
cursor mixture. To prepare the partially crystalline zeolite
product, the combined seed slurry and precursor reaction mixture
is reacted for a period of from about 15 to 180 minutes at a
temperature of about 90 to 110C. whereat a partially crystalline
product was formed which contains from about 10 to 100% crystalline
zeolite which is theoretically obtainable from the reaction
mixture if the reaction were permitted to run to completion. As
indicated above, water is then added to the reaction mixture to
terminate the crystallization procedure and to further dilute
the excess alkali metal silicate present. Generally sufficient
water is added to lower the temperature at least to 50C and to
dilute the silicate to a level wherein the aqueous solution of
silicate contains from about 7 to 3~ sodium silicate.
The reaction slurry, after the partial crystallization
has taken place, is then combined with an acid gelling agent.
These gelling agents may be selected from the group consisting
of mineral acids such as sulfuric acid, hydrochloric acid -
or nitric acid. Gelling agents such as carbon dioxide may also ~-
be effectively used to gel the excess silicate. Furthermore,
it is contemplated that acid aluminum salts such as alum may be
utilized. Furthermore, it is sometimes found that a combination
.
of gelling agents including acid and alum may be effectively
used.
Furthermore, it is contemplated that additional catalyst
ingred~ients, such as clay, may be effectively added to the
gelled compositions in amounts ranging from about 25 to 50
by weight of the finished catalyst composition.
The gelation step is preferably conducted on a continuous
basls and in connection with a c~ntinuous crystallization
procedure such as outlined above. Furthermore, it is con- ~ -
tem]~l~ed that the gelation p~ocedure may be conducted on a
- 7 -
`.,
~0370~L~
batchwise basis, however, the primary benefit obtained in the
present invention results when a continuous overall catalyst
preparation procedure is conducted.
Subsequent to gelation of the catalyst composition,
the solid catalyst is recovered from the mother liquor and
washed to remove soluble salts. Furthermore, the catalyst
is ion exchanged with dilute ammonium salts such as dilute
ammonium sulfate to further reduce the sodium level of the
catalyst. The catalyst is then slurried and formed into catalyst
particles of a desired configuration. In a particularly pre~
ferred practice o~ the invention, the catalyst slurry is spray
dried to form microspheres having a particle size ranging from
about 50 to 300 microns. Alternatively, the catalyst may be
pilled or formed into granules having particle sizes on the order -
of 1/8 to 1/4 inches in diameterO Subsequent to spray drying
the catalyst may be further ammonium exchanged to remove addition-
al alkali metal salts to a level below about .6~ Na20. The -
catalyst may be ion exchanged with polyvalent metal ions such as
rare earth ions to further enhance the stability of the catalytic
2~ properties of the catalyst composition.
The catalysts prepared in accordance with the present
invention will generally contain from about 15 to 35~ by weight
zeolite calculated on total weight basis. Furthermor~, the ;
catalyst may contain a matrix which is essentially synthetic
or the matri~ may contain substantial quantities of clay such
: as kaolin. The catalysts prepared in accordance with the
present invention wherein faujasite is used as the zeolite and
rare earth metal ions are exchanged therein are particularly
effective for the catalytic cracking of h~idrocarbons. These
3Q catalysts possess both good catalytic activity and good attrition
properties ~hen utilized in commercial cracking units. -
Having described the basic aspects of the present ~ -
' , '' :,.
-- 8 --
3 :037~14
invention, the following examples are given to illustrate specific
embodiments thereof.
Example I
. . .
A series of catalyst samples was prepared usiny the
teachings of our invention.
(a) Three samples of faujasite precursor reaction
mixture as follows:
To 284 y of sodium aluminate solution containing
0.333 mole of A12O3 and 0.466 mole of Na2O, were added slowly
with stirring to 1422 g of sodium silicate solution ha~ing
a density of 1.360 g/cc and 954 g of water.
(b) A zeolite seed preparation was prepared as follows:
158 g o~ NaOH were added 558 g of H2O. This solution
was heated to 80~C. at which point 26 g of C-31 A12O3 (65%
A1203) was added slowly and stirred until completely dissolved.
The solution was cooled to 15 C. and maintained at this temper-
ature while 555 g o~ sodium silicate solution (27~ SiO2, 8
N2O) was slowly added. The resulting seed solution was allowed
to sit for 16 hours prior to use.
(c) 248 g samples of the seed preparation were added
to each o~ the above reaction mixture samples. The mixtures ~;
were heated at reflux (110C) for 1.5 hours.
(d) The heating was stopped and each sample was
~;; diluted with 4840 g of water having a temperatuxe of 40C. This
addition of water resulted in dilution of the sodium silicate
solution~in the reaction mixture to a level of 5.5% silica.
e) The mixtures were cooled to 80F and gelled with
;8% aluminum sulfate solution until the pH of the gelled mix~ures
~ reached~9.0 tSamPle 1), 10.0 (Sample 2)/ and 10.7 (Sample 3),
~ respectively. The samples were then aged for 1/2 hour. Additional
aluminum sulfate (5~ solution) (50-100 g) was added to give a
~ 9 ~
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~037~1~
total silica to alumina ratio of 3:1.
(f) The samples were washed with 1~ 1H4)2S04 and
rare earth exchanged with a rare earth C13 to yield catalyst
samples having the following characteristics: , ~ '
Table' I
wt. % wt. % rare Surface Area
Sample No. Zeolite ear'th oxide m2/a
. _
31 7.7 174 ' ,
2 27 6.~ 158
3 35 8.0 200
The zeolite was a type Y zeolite having a SiO2/A12O3 ' ~ '
of 5/1.The zeolite content in the above samples was determined ~, ,
by x-ray dif~raction. '
Examp'le' II
A larger catalyst sample was prepared as follows: ;~ '
To 9.94 pounds of a sodium aluminate solution, which , ', ,
contained Q.333 mole of A12O3 and 0.466 mole of Na2O, 33.6 ~ ~
pounds o~ H2O and 58.3 pounds of sodium silicate solution - ,~,
which contained 27% by wt. SiO2 and 8.2~6 by wt. Na20, were
added. To this mixture 8.68 pounds of the zeolite seed pre- `,
paration, prepared by the procedure of Example I (b), were
added. The mixture was heated at reflux (110C) for 1.5 hours. ' ,'
The heating was stopped and 175 pounds of H2O were
added to dilute the reaction mixture~ The concentration of `~' ' '
excess silicate in the reaction mother liquid was 5.5 wto % SiO2. ''
The mixture was cooled to 80F and gelled by the addition of
,, . - .
70 pounds of 5% aluminum sulfate solution. The pH of the mixture ,
; was 10.7. The mixture was aged for 1/2 hour at a temperature of ~ -
~ 80F.
After aging, an additional 2 pounds of A12(SO~)3 ',
; solution were added to yield a total SiO2/A12O3 ratio of 3/1. ,~ ' ' '
The product was washed with 10% (MH4)2SO4 and rare ' '
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:
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l037a~
earth exchanged with rare earth C13. The product was spra~
dried to yield a catalyst haviny the following properties: ,
T ble'II
~ Zeolite* Rare earth Surface Area
Sample No. ' (wt'.)' oxide (wt.) (m2/g) ____
4 32 4.0 413
*wt. % type Y zeolite calculated o,n basis of SiO2 and A12O3
content.
''E'xamp'le'III
The catalyst samples prepared in Examples I and II
were evaluatad for activity and selectively as catalytic cracking
catalysts in a pilot unit operated at 920F, a catalyst to oil
ratio of 4, and a we-ight hourly space velocity (WHSV) of 40 and
60. The feed stock was a West Texas Devonian gas oil having a
boiling range of 653 to 931F. ,,~,
Prior to testing, all catalyst samples wer~ deactivated
by steaming at 1520F using 20~ steam, at atmospheric pressure
~or 12 hours. The results are set forth in Table III~
' T'able''I'II_ '
20Sample No. ''%''Coke ~ Converstion ~ ~-
1 5.3 88
2 3.9 82.6
3 ~.0 94 - ~ ', -
4 ~ 2.78 84.6
~ .
~ ~ ~ For purposes of comparison a sample of commercial
;~ ~ catalyst (CBZ-I) which contained rare earth exchanged type Y
,,
zeolite was evaluated and compared with Sample 4 as set forth
n~Table I~
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T:able IV
Sample No. 4 4 CBZ-l
WHSV 40 60 40
Conversion, Vol. % 83.0 82.0 72
H2, wt. % .043 .052 .037
Cl ~ C2, wt. % 2.07 2.21 2.2
Total C3, vol- % 12.7 10.7 10.1
C3=, vol. gO 11.4 9.5 8.3
Total C4, vol. % 16.4 15.7 11.2
C4=, vol. % 5.7 5.7 3.3
iC4, vol. % 9.5 9.1 6.8
C5 + Gasoline, vol. % 69.5 66.1 52.4
Coke, wt. % 4.9 5.9 5-7
" . . , - ", . ,-
Gasoline/Conv. 0.83 0.81 0.80
gO Zeolite Promoter 32 32 16 : .
% Rare earth oxide 7.20 7.20 3.37 :
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