Note: Descriptions are shown in the official language in which they were submitted.
The present invention relates to the production of
catalytic cracking catalysts and more specifically to
aluminum exchanged type Y zeolite containing catalysts
which produce high octane cracked gasoline.
zeolite promoted cracking catalysts which produce
substantial yields of gasoline by the catalytic
cracking of petroleum gas oil feedstocks have been in
commercial use for several years.
Canadian 848,966 describes a~catalytic cracking
catalyst which contains a thermally stahilized type Y
zeolite, i.e. Z14US, which may be exchanged with a
variety of metal cations including aluminum ions. The
gasoline fractions produced usin~ Z14US zeolite
containing cracking catalyst have good octane ratings.
U.S. 3,293,192, 3,375,065, 3,402,996, 3,4ag,07o
and 3,5~5,611 describe methods for preparing thermally
stabilized type Y zeolites suc,h as ~ S zeolite. ~he
methods disclosed in these references typically
involve exchan~e oP a sodium type Y zeolite with
ammonium ions, calcination and further ammonium/metal,
cation exchange.
U.S. 3,455,842 describes preparation of an
ammonium~aluminum exchange type Y æeolite which,is
used in the preparation of catalytic cracking
catalysts.
~ he ~eolite containing cracking catalysts prepared
by prior art methods produce significant yields of
cracked gasoline. However, it is frequently observed
that most h~ghly active rare-earth exchanged zeolite
cracking catalysts produce large quantities of
gasoline of medium octane rating. ~onversely,
hydrogen exchanged zeolite cata]ysts which are
particularly selective for the production of high
8 3L ~
octane gasoline fractions frequently exhibi~ lower
activity.
Accordingly, it is an object of the present
invention to provide a cataly~ic cracking catalyst
which is bo~h highly active and selective for ~he
production of high octane gasoline.
It is another object to provide a method for
preparing commercial quantities of 2eolite promoted
cracking catalysts which are capable of cracking
petroleum feedstocks at a high rate of conversion to
obtain substantial yields of high octane gasoline.
It is yet another object to provide a thermally
stable highly active aluminum exchanged type Y zeolite
which contalns very low levels of sodium ion.
It is still another object to provide an
economically feasible procedure for pro~ucing aluminum
exchanged thermally stahili~efl zeolites which have
particularly low residual sodium content.
~ hese ~nd still further objec~s of the present
invention will become readily apparen~ to one skilled
in the art ln the ~ollowing detai.led description and
examples.
Broadly~ my.invention contemplates the preparation
of novel. catalytically active aluminum exchanged
crystalline alumino-silicate type Y zeolites which may
be used to prepare active, h~gh octane gasoline
selective cracking catalysts.
More specifically, and in accordance with the present
teachings, a process is provided for preparing a cracking cata-
lyst which comprises: ~
(a) Exchanging a sodium type Y zeolite with an ammonium
salt solution to lower the sodium content of said zeolite to
below about 4 percent by weight Na20;
(b) calcining the ammonium exchanged zeolite at a tempera-
ture o~ from about 537 to 815C;
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~61~
(c) mixing said calcined 2eolite with an inorganic oxide
matrix and water;
(d) spray drying said mixture; and
(e) reacting said spray dried mixture with an acid aluminum
salt solution having a pH of from about 2.0 to 3.7 to lower the
sodium content to ~elow about 1.0 pexcent by weight Na20.
~ he sodium type Y zeolite used in the practice of
the present invention posse~ses a ~ilica to alumin3
ratio of from about 4.~ to 5.2 and a unit ~ell
dimension o~ from about 24.60 ~o 24.65. ~ypical ~oda
Y zeolites contain from ahout 20 to 22 percent by
weight alumina (A1203), 68 to 65 percent by weight
~ilica ~SiO2), and 13 to 12 percent by weiqht sodium.
(Na20). Sodium type Y zeolites are readily obtained.
from commercial ~ources.
~ he sodium salt solution which is used to reduce
the ~odium levei of the initial 60dium Y zeolite is
preferably ammon~um ~ulfate. Rowever, it is
contemplated that solutions of ammonium chloride or
am~on~um nitrate may be used. An ammonium 6al~
solution contains typically from about 3 to 10 percent
by weight o~ the ~alt dissolved ln water. ~he
ammonium ~alt solution ls contacted with the ~odium Y
zeolite for a period of from about 10 to 120 minutes,
preferably at a temperature ranging from about 60 to
100~. ~n order to obtain the desired level of soda
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`` 116~81~
removal, i.e. reduction of the Na7O content to below
4 percent by weight, preferably below 3 percent by
weight. Typically the sodium Y zeolite is contacted
with from about 1 to 3 batches of the ammonium salt
solution.
Subsequent to contact with the ammonium salt
solution, the NaNR4Y zeoIite is heated, i.e.
calcined, at a temperature of from about 538 to
~15~. Preferably, the calcination is conducted for a
period of from about 120 to 180 minutes utilizing
conditions wherein the zeolite is maintained in a
self-steaming condition. During the calcination step,
the initial unit cell dimension of the sodium Y
zeolite is reduced by about 0.2 ~, that is, the unit
cell dimension of the calcined zeolite will be in the
range of from about 24.45 to 24.52 A.
The calcined zeolite is then subjected to
treatment (exchange/reaction) with an acid aluminum
salt solution. Preferahly, the salt solution is
aluminum sul~ate which has been acidified with
~ufficient sulfuric acid to obtain a p~ o from about
3~7 to 2.0 and preferably 2.7. While aluminum sul~ate
ls the preferred acid salt, it is contemplated that
aluminum chloride or aluminum nitrate may be u~ed with
appropriate additions of hydrochloric or nitric acid.
As a result of the contact with the acid aluminum
salt, the rest of the residual sodium ions present in
the calcined zeolite are exchanged with aluminum
ions. Preferably, the contact with the acid aluminum
salt is repeated using successive fresh batches of
aluminum salt solution until the sodium content of the
zeolite is reduced to helow 1 percent by weight Na2O
and preferahly below 0.8 percent by weight ~a2O. As
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l l 61 ~-~8
a result of this exchange step, the unit cell of the
calcined zeolite is 24~52 to 24.a5. Furtherm~re, it
is noted that as a result of the processing described
above, the alumina content of the zeolite is-from
about 23 to about 13 pexcent by weight depending on
the pH of the exchanging slurry. It is also ~bserved
that as alumina is removed from the zeolite, the
overall surface area of the zeolite, which is
initially 650 m2/g, is increased~. This indicates
that the overall crystalline structure of the æeolite
remains intact. In many instances zeolites which are
subjected to calcination and acid exchange conditions
lose crystallinity.
Subsequent ~o exchange with the aluminum salt
solution, the zeolite is subjected to exchange with an
ammonium ~alt solution, typically, ammonium sulPate.
This ammonium sulfate exchange results in further
sodium removal to produce a zeolite composition which
contains less than about 0.5 percent by weight Na2~.
~he zeolites prepared by the procedure described
abo~e are advantageously combined with an inorganic
oxide matrix to obtain highly active, gasoline
selective cracking catalyst. ~ypic~lly, the matrix
component comprises clay and an inorganic oxide binder
such as silica, alumina, silica-alumina sols, and
silica~ alumina, silica-alumina gels. ~ombining of
the zeolite with the matrix component may be achieved
by the procedures set forth in U.S. patents 3,957,689,
3,867,308, and 3,91~,619. Hydrocarbon cracking
catalysts which include the zeolite of the present
invention contain from about 30 to 40 percent by
weight zeolite, from about 45 to 35 percent by weight
clay and the balance inorganic oxide sol or gel
binder. Furthermore, the catalysts may contain
1 1~18~
components such as alumina and minor ~uantities of
platinum which result in the preparation of catalysts
which oxidize carbon monoxide andjor control sulfur
emissions from the catalytic cracking process.
Furthermore, it is contemplated that the novel
aluminum thermal exchanged zeolites of the present
invention may be combined with other æeolites such as
rare-earth exchanged and type Y zeolites to obtain a
catalyst having multiple zeolite promoters.
The catalysts obtained using my novel zeolite are
highly active. Furthermore, the catalysts are capa~le
of producing gasoline fractions which possess an
~nusually high octane when the catalytic cracking
process is operated at relatively high conversion,
i.e. from about 60 to 70 percent conversion. ~he
gasoline fractions obtained using the present
catalysts will possess an octane rating of from abo~t
90 to 91 re~earch and from abo~t 7~ to 79 mo~ar.
Having described the basic aspects of the present
lnvention, the following examples are glven ea
illustrate specific preferred embodiments.
EXAMPI.E I
la) A sodium type Y zeolite (~aY) was exchanged
with ammo~ium sulfate solution to obtain a
sodium/ammonium type Y zeolite (Na,NH4Y~ which
contained 3.55 weight percent Na2O. The Na,N~Y:
was heated at 1250F for 3 hours to obtain a calcined
Na,NH4Y which has the following properties:
Surface Area - 757 m2/g
Crystallinity - 97% of standard
Unit Cell - 24.49 A
SiO2 - 71.99 wt.%
A12O3 - 23.46 wt.%
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(b) The calcined Na,N~T4Y zeolite prepared in
(a) above was treated with a n.os M aluminum sulfate
solution for 4~ minutes at pH 3.3. This product was
then exchanged twice with dilute ammonium sulfate
solution to obtain a zeolite having the ~ollowing
properties:
Crystallinity - 89% of standard
Na2O - n.7~ wt.%
Si~2 - 73.~ wt.%
A12O3 - 23.62 wt.%
(c) A second sample of the calcined ~a, NH4Y
prepared in (a) above was treated with a 0.05 M
aluminum sulfate solutiQn for 45 minutes at pH 2.6 a~
95C, followed by two exahanges with dilute ammonium
sulfate solution~ The resulting zeolite has the
following properties~
Crystallinity - 105~ of standard
Na2~ ~ 0.25 wt.%
5i~2 ~ 80.fi wt.
Al~O~ - 16.1 wt.
~ ~ ~181 ~
Example II
(a) ~ sample of cracking catalyst was prepared
and evaluated fo~ cracking activity which contained 4n
weight percent of the zeolite prepared in Example ~,
paragraph (c). ~he catalyst included a
clay/silica-alumina sol matrix which comprised 35
weight percent clay and 25 weight percent silica. The
catalyst sample had the following properties after
treatment with 20 percent steam,~at 1520F for 120 hours.
Na2O - 0.17 wt.% 2
Surface area 258 m /g
N2 Pore Volume - 0.22 cc/g
~2 Pore Volume - 0.42 cc/g
Microactivity* - 67.5 volume % conversi~n
unit Cell - 24.22 A
* Determined at 16 wt. hourly space velocity.
3 catalyst/oil ratio at 900F.
(b) A catalyst sample was prepared by combining
40 weight percent of the calcined ~a,NH4y zeolite of
~xample I ~a) in the matrix desc:ribed in ~a) above.
The catalyst was spray dried, and then washed with
water at 140F. ~en pounds of the washed catalyst was
rinsed three times at 140F with 10 pounds dilute
2S (3Be') am~onium sulfate solution at p~ 5. ~e
catalyst was then washed with dilute ammonium
hydroxide solution at pH 7.5.
(c) ~ catalyst sample was prepared by a procedure
similar to that set forth in (b) above. ~owever,
after washin~ with water, 10 pounds of thq catalyst
was mixed with 35 pounds of aluminum sulfate solution
which contained 0.5 weight percent A12O3. The
exchange was conducted at pH 2.7 and 140F. The
catalyst was then washed with ln pounds of dilute
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ammonium s~lfate solution at pFI 5. ~he catalyst was
reslurried with 34 pounds of the aluminum sulfate
solution, and finally washed with dilute ammonium
h-ldroxide 501ution.
td) A procedure similar to that set forth in
paragraph (c~ was followed. ~owever, after washing
with water 10 pounds of the catalyst was rinsed three
times with 34 pounds of aluminum sulfate solution
which contained 0.5 weight perce~t ~12O3 at p~
2.6. ~he catalyst was then ~ashed with dilute
ammonium hydroxide solution at pR 7.5.
The catalysts prepared in paragraphs (b), (c) and
td) of Example II had the fo]lowing properties:
Catalyst (Example) II(b~ ) III(d)
15 ~otal Volatiles (wt.%~ 10.20 11.0310.33
Na2O (wt.%) 2 0.42 0.210.78
Surface Area (m /g) 195 20~ 2no
Microactivity (% conversion)65.4 68.7
~ II
To demonstrate the octane enhancing selectivity of
the catalysts of the present invention, a sample of
the catalyst prepared in Example Il(c) was compared
with a sample of the non-aluminum sulfate exchanged
catalyst of Example ~Itb). ~he following fluid
crackin~ catalyst pilot unit data was developed at 40
wt~ hourly space velocity, 4 catalyst/oil ratio at
950F after deactivity the catalysts using 20 percent
steam at 1S20F for 12 hours:
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Catalyst (Example~- Il(c) IJ~b)
Conversion, ~101.% 620 n 62.0
C5 + Gasoline, vol.~ fresh feed52.5 54.0
Octane No.
- 5 Research 90.3 88.~.
Motor 78.9 77.9
Light Cycle Oil, vol.~ fresh feed 25.9 26.5
Coke, Wt.% fresh feed 2.7 2.7
It is concluded drom the above data that the
aluminum sulfate exchanged catalyst of the present
invention (Catalyst Il(C)) produces gaSoline of hiqher
octane rating than the non-aluminum sulfate exchanged
t~ly ~;~t~llyst Il (b) ) .
