Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
Background of the In~rention
The use of zeolite promoted cracking catalysts is
well known. U.S. Patent 3,140,249 to Plank et al.
is typical of the early patents in this area. These
patents generally disclose the use of a faujasitic type
zeolite having a silica to alumina ratio of about 3 to 6
that has exchanged therein a fairly substantial quantity
of rare earth oxides, distended in a matrix such a~
silica, silica-alumina, silica-zirconia, alumina, etc.
The preferred catalyst comprise the rare earth exchange
faujasitic zeolites in a silica-alumina matrix.
Continuing efforts have been made to improve these
catalysts by making them more stable, more resistant to
high temperature and more economical. One of the
recurring problems is the use of the relatively rare and
quite costly rare earth salts in t~e preparation of these
catalysts. The process of the instant application prepares
a stable active zeolite containing catalyst that minimizing
~he amount of rare earth contained therein.
0 Brief Description of the Invention
.
I have found that an exceptionally stable and active
~catalyst can be prepared by suspending a faujasitlc type
zeolite with a silica to alumina ratio of greater than
7 to 20 in a suitable matrix. The zeolite is present as
about 5 to 50 percent, preferably about 10 to 30 percent of
the composite and contains less than 10 percent of
rare earth.
Detailed Description of the Invention
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The first step in our process is the preparation of
the zeolite having a silica to alumina ratio of greater
than 7 to ahout 20. The method for preparing the zeolite
is not part of this invention it is disclosed in United States
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Patent 3,595,611 to McDaniel et al issued July 27, 1971.
Briefly the process comprises treatlng a faujasitic type
zeolite that hasbeen subjected to an ion exchange to
reduce the Na2O content to less than 4%, followed by calcin-
ation at a temperature in excess of 1200F. for a period of
about 0.1 hours. This stabilized faujasite is then treated
with a dilute mineral acid to remove a portion o~ the alumina
and shift the silica to alumina ratio from about 3.5 to 6
to greater than 7 to about 20.
The critically important features of -this process
are the preparation of the stabilized zeolite by the com-
bination of ion exchange and calcination steps followed by
the acid treatment to remove a portion of the alumina. The
product recovered from this treatment is a zeolite having
a high degree of stability and relatively low ion exchange
capacity.
The next step of the process is incorporation
of the rare earth or other cations into the partially de-
aluminated zeolite by ion exchange. This is accomplished by
conventional ion exchange techniques. Because of the low
ion exchange capacity the amount of rare earth or other ions
in the zeolite is relatively low, generally in the order
of 1 to 10 percent dry weight.
Crac~ing catalysts normally contain rare earths
exchanged into the zeolite. However, other cations such
as magnesium also give satisfactory results.
Thus, in accordance with the present teachinys
a method is provided for the preparation of stable crystalline
zeolite which comprises exchanging a sodium Type ~ zeolite
which has a silica to alumina ratio of about 3.5 to 6 with
an ammonium salt to reduce the Na2O content to less than
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percent by weight. The zeolite is then exchanged with a
solution of rare earth ions -to proviae a rare earth oxide
content of about O . 5 to 4 percent by weight. The zeolite
is then washed to remove excess salts and heated to a
temperature of about 700 to 1600F. The zeolite is then
contacted with a dilute solution of a mineral acid to remove
alumina therefrom and to increase the silica to alumina ratio
in the range of about 7 to 2~ and subsequently exchanging
the zeolite ~ith a solution of metal ions selected from the
group consisting of rare earth and magnesium ions ~o impart
a concentration of metal îons of from a~out l to lO percent
by weight.
In the next step of the preferred process of the
invention the zeolite in the rare earth or other cation form
is distended into an inorganic oxide matrix. In manner the
zeolite crystals are suspended in and distributed
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~hroughout the matrixO The catalyst-matrix suspension can be
readily prepared by dispersing the æeolite in the rate earth
form in a suitable siliceous sol a~d gelling the sol by
various means. In addition, the zeolite may be dispersed
in a cogel of silica and an oxide of a second metal.
Examples of suitable cogels include silica-alumina, silica~
magnesia, silica-zirconia9 silica-titania, as well as
tertiary combinations such as silica-alumina-zirconia,
silica-alumina-magnesia, silica~magnesia-zirconia, etc.
T&e preferred cogels include silica-alumina and silica~
magnesia, with silica-alumina being particularly preferred~
In addition, the matrix may contain a considerable amount
of clay that is normally added to the sodium silicate
solution prior to forming the cogel with alumina~ magnesia;
etc.
These gels and cogel will generally comprise a major portion
of silica and a minor portion of the other oxide or vxides.
The silica content of the siliceous gel or cogel matrix will
generally be in the range of 55-100 weight percent, preferably
; 20 60~90 weight percent with the other metals in the range of
5-45 weight percent, preferably 10-40 weight percentO
If clay is added as a component of the matrix it is
only present in the amount of 10 to 70 percent.
The qilica-alumina hydrogels can be produced by any
number of known methodsO For example, a hydrous precipitate
of silica can be prepared by mixing the solution of sodium
silicate with an acid such as sulfuric acid or with carbon
dioxide to produce a slurry having a pH below 9~ usually
below 7. A solution of an alumlnum salt such as aluminum
sulfate~ for example~ i,4 then added and the pH of the mixture
is ad~usted to above 4 by the addition of an alkaline
material such as ammonia in order to precipitate the alumina.
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As pointed out above, in addition it is
contemplated that the matrix can comprise natural or
synthetic clays such as kaolin type clays, montmorillonite,
bentonite, halloysite, etc.
The zeolite-matrix compositions are prepared by
intimately admixing the aforesaid described zeolite with
the siliceous hydrogelS clay or mixtures thereof and
thereafter obtaining a composite product comprising the
zeolite component uniformly distributed throughout and
suspended in the inorganic oxide matrix.
The zeolite component of the catalyst is normally
present in the amount of about 5 to 50 percent, preferably
about 10 to 30 percent.
My invention is illustrated by the following specific
but nonlimiting examples~
Example 1
The zeolite described in U.S0 Patent 3,595,611 and
designated PCY was prepared by treating a faujasite having
a silica to alumina ratio of about 3.5 to 5 with a ;
combination of ammonium ion exchange and metal ion exchangeO
The zeolite was first exchanged with an ammonium salt
solution to reduce the Na20 content to about 2.5 to 3.5
percent. The zeolite was then filtered and the cake
returned to the solution of a salt contaiDing rare earth
or other cations sufficient to provide 0.5 to 15 percent
rare earth o~ide or the equivalent amount of other cations
to the ~eolite. The product was then filtered, washed free
of e~cess salt and heated at a temperature of about 700
to 1600Fo The product was then cooled and exchanged with
- 30 an ammonium salt solution to reduce the Na20 content to
- less than 1 percentO
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A 100 gram sample of this zeolite was treated with a
dilute (0.1) normal solution of nitric acid a~ a temperature
of 30Co for a period nf 4 hoursD The zeolite was
filtered and again treated with nitric acid. A total of
0.75 moles of nitric acid was used in this treatment. The
zeolite was then recovered, washed free of dissolved salts
and dried. The analysis of the zeolite in weight percent
was as follows: Na20 less than 0.2; SiO2 B3.2; A1203 12.6;
rare earth oxides lo 5.
The zeolite was prepared as a catalyst component by
dry mixing the zeolite with a semi-synthetic commercial
cracking catalyst having a low activity. The semi-synthetic
catalyst contained 60 percent silica-alumina and 40
percent clay. The physical blend of the two components
was formed into pills and the catalytic activity was
determined using a microactivity tes~. In this test the
samples to be tested are placed in a reactor and heated to
a temperature of 900F. in the presence of a WeSt Texas
Gas Uil Feed. The catalyst oil ratio was 5.88 and the
weight hourly space velocity was 16. In this run the
catalyst prepared to contain 10% of our novel zeolite,
designated catalyst Cg was compared with a semi-synthetic
catalyst that contalned no zeolite designated catalyst B
and with a catalyst containing 10% of the ultra stable
fau~asite designated catalyst Ao The data collected in
the series of runs is set out in the table below.
TABLE I
Catalyst B _ C_
Conversion volume percent 29.08 46.82 61.54
H2 weight percent 0.0540.045 0-059
Cl weight percent 0.0990.092 0.146
C2 weight percent 0.1040.060 0,211
C3 volume percent 0.360.44 0.88
C4 volume percent 7.709.34 11.7
C5 ~ gasoline volume 21.9038.64 52.16
percent
Coke weight percent 1.361.14 1.42
It is apparent from a review of this data that the
catalyst of the instant application has a good conversion
and a high conversion to gasoline with a small conversion
to coke. This result was achieved even though the
catalyst contained only 0.1~ rare earth oxide.
Example 2
A run was completed in which the amount of rare earth
oxide in the zeolite was increased by an additional rare
earth exchange
A ~o~al of 25 grams of the zeolite described in
Example 1 was exchanged with a rare earth chloride
solution containing 10 grams of rare earth chlorlde
(asRE 23) per 100 ml. using ratios of zeolite to rare earth
to water of 1 to 1 to 10. The exchange was carried out for
30 mlnutes at a temperature of about 90C. The zeollte
was wasned free of dissolved salts and dried. The
analysls of the zeolite ln weight percent was as follows:
Na2O - O.1; rare earth oxide 7.1; alumina - 10.2;
silica - 82.6. A physical blend of 10~ of the zeolite
and 90% of the low activity commercial semi-synthetic
` cracking catalyst was prepared and pills were foxmed
from this mixture. The microactivity of this ca~alyst
(designated Catalyst D) was compared with the catalyst
designated A of Example 1. The results of this comparison
are set out in the table below.
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Table II
Catalyst A D
Conversion volume percent 46.82 71.93
H2-weight percent 0 045 0.052
Cl weight percent 0.092 0.243
C2 weight percent 0.060 0.260
C3 volume percent 0.44 1.22
C4 volume percent 9.34 12.72
C + gasoline volume 38.64 60.56
5 percent
Coke weight percent 1.14 1.89
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It is apparent from review of these data that there is a
substantial improvement in conversion and a substantial
improvement in gasoline recovery when the amount of rare
earth in the zeolite is increased.
Example 3
In this example the product of Example 1 was given an
additional exchange with a mag~esium chloride solution.
A total of 25 grams of the zeolite was exchanged with
a magnesium chloride solution containing 10 grams of
mag~esium chloride per 100 ml. The zeolite to magnesium
chloride to water ratios were 1:1:10. The zeolite was
washed free of excess salt and dried. The analysis of
the zeolite in weight perc~nt was as follows: Na2O - 1.0;
RE2O3 - 1.5; A1203 - 10.4; SiO2 - 87; MgO - 1Ø A
catalyst was prepared from this zeolite by physically
blending `10% of the zeolite and 90% of a low activity
commercial semi-synthetic cracking catalyst. The
mixture was formed into pills and the microactivity test
was carried out under the same conditions as in Example 1.
The product of this run was identified as catalyst E
and was compared with the catalyst A of Example 1.
The data collected in this run is set out in the table
below.
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Table III
Catalyst A E
Conversion volume percent46.82 71.68
H2 weight percent 0.045 0.062
Cl weight percent 0O092 0.195
C2 weight percent 0.060 0.253
C3 volume percent 0.44 1.27
C4 volume percent 9.34 12.76
C5 ~ gasoline volume percent 38.64 60.43
Coke weight percent 1.14 1.39
It is apparent from the data that a catalyst containing
as little as 0.1% magnesium gives excellent conversions.
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