Molecular sieve abstract
A crystalline, gallioaluminosilicate molecular sieve having the
faujasite structure is synthesized by mixing a substantially gallia-free
aluminosilicate hydrogel with a galliosilicate solution substantially
free of alumina to form a mixture having the following oxide mole
ratios of components and then crystallizing the resultant mixture,
usually in 3 days or less, under relatively quiescent conditions.
Molecular sieve claims
I claim:
1. A process for synthesizing a crystalline, gallioaluminosilicate
molecular sieve having the faujastie structure and a silica-to-(alumina+gallia)
mole ratio between 3 and about 10 which comprises:
(a) mixing a substantially gallia-free aluminosilicate hydrogel
having the following oxide mole ratios of components
with a galliosilicate solution substantially free of alumina, said
solution having the following oxide mole ratios of components
to form a mixture of said hydrogel and said solution, wherein said
mixing is carried out by adding a sufficient amount of said galliosilicate
solution to said aluminosilicate hydrogel so that said mixture of
said solution and said hydrogel contains between about 1 and about
40 weight percent of said galliosilicate solution; and
(b) crystallizing said mixture in the absence of substantial agitation
to form a gallioaluminosilicate molecular sieve having the faujasite
structure and a silica-to-(alumina+gallia) mole ratio between 3
and about 10 wherein said crystallization takes place in less than
3 days.
2. A process as defined by claim 1 wherein said aluminosilicate
hydrogel is formed by dissolving sodium aluminate in an aqueous
solution of sodium hydroxide and adding a source of silica thereto.
3. A process as defined in by claim 2 wherein said galliosilicate
solution is formed by dissolving gallium oxide in a an aqueous solution
of sodium hydroxide and adding a source of silica thereto.
4. A process as defined by claim 3 wherein the source of silica
used in forming said aluminosilicate hydrogel and said galliosilicate
solution comprises a silica sol.
5. A process as defined by claim 1 wherein said mixture is crystallized
at a temperature between about 7020 C. and about 150.degree. C.
6. A process as defined by claim 1 wherein said mixture is crystallized
at a temperature between about 90.degree. C. and 110.degree. C.
7. A process for synthesizing a crystalline, gallioaluminosilicate
molecular sieve having the faujasite structure and a silica-to-(alumina+gallia)
mole ratio between 3 and about 10 which comprises:
(a) mixing a source of alumina, a source of silica, a source of
sodium and water to form an aluminosilicate hydrogel substantially
free of gallia, said hydrogel having the following oxide mole ratios
of components
(b) adding to said hydrogel a galliosilicate solution substantially
free of alumina, said solution having the following oxide mole ratios
of components
to form a mixture of said solution and said hydrogel containing
between about 1 and 40 weight percent of said galliosilicate solution,
said mixture having the following oxide mole ratios of components
wherein said galliosilicate solution is prepared by mixing a source
of gallia, a source of silica, a source of sodium and water;
(c) agitating said mixture at ambient temperature for between about
one hour and two days after which time the temperature of said mixture
is raised during agitation to between 90.degree. C. and 150.degree.
C.; and
(d) crystallizing said mixture in the absence of substantial agitation
at a temperature between about 90.degree. C. and 150.degree. C.
to form a gallioaluminosilicate molecular sieve having the faujasite
structure and a silica-to-(alumina+gallia) mole ratio between 3
and about 10 wherein said crystallization takes place in less than
3 days.
8. A process as defined by claim 7 wherein said source of gallia
comprises gallium oxide.
9. A process as defined by claim 7 wherein said source of sodium
comprises sodium hydroxide.
10. A process as defined by claim 7 wherein said source of silica
comprises a silica sol.
11. A process as defined by claim 7 wherein said source of alumina
comprises aluminum oxide or sodium aluminate.
12. A process as defined by claim 7 wherein step (c) is carried
out at a temperature between about 90.degree. C. and about 110.degree.
C.
13. A process as defined by claim 7 wherein said Na.sub.2 O/Ga.sub.2
O.sub.3 ratio in the solution of step (b) is between about 8 and
about 15.
14. A process as defined by claim 7 wherein the aluminosilicate
hydrogel formed in step (a) has the following oxide mole ratios
of components
15. A process as defined by claim 14 wherein the galliosilicate
solution of step (b) has the following oxide mole ratios of components
16. A process as defined by claim 15 wherein the mixture of said
aluminosilicate hydrogel and said galliosilicate solution has the
following oxide mole ratios of components
17. A process as defined by claim 7 wherein said gallioaluminosilicate
molecular sieve having the faujasite structure has the following
composition expressed in terms of oxide mole ratios in the anhydrous
state
wherein a equals 0.5 to 0.99 b equals 0.01 to 0.5 c equals 3
to 7 d is approximately 1.0 and a+b equals 1.0.
18. A process of synthesizing a crystlaline, gallioaluminosilicate
molecular sieve having the faujasite structure ad a silica-to-(alumina+gallia)
mole ratio between 3 and about 10 which consists essentially of:
(a) mixing a substantially gallia-free aluminosilicate hydrogel
having the following oxide mole ratios of components
with a galliosilicate solution substantially free of alumina, said
solution having the following oxide mole ratios of components
to form a mixture of said hydrogel and said solution, said mixture
having the following oxide mole ratios of components
wherein said mixing is carried out by adding a sufficient amount
of said galliosilicate solution to said aluminosilicate hydrogel
so that said mixture of said solution and said hydrogel contains
between about 1 and 40 weight percent of said solution; and
(b) crystallizing said mixture at a temperature between about 70.degree.
C. and about 150.degree. C. in the absence of substantial agitation
to form a gallioaluminosilicate molecular sieve having the faujasite
structure nd a silica-to-(alumina+gallia) mole ratio between 3 and
about 10 wherein said crystallization takes place in less than
3 days.
19. A process as defined by claim 18 wherein said gallioaluminosilcate
molecular sieve having the faujasite structure has the following
composition expressed in terms of oxide mole ratios in the anhydrous
state
wherein a equals 0.5 to 0.99 b equals 0.01 to 0.5 c equals 3
to 7 d is approximatley 1.0 and a+b equals 1.0.
20. A process as defined by claim 18 wherein step (b) is carried
out at a temperature between about 90.degree. C. and about 110.degree.
C.
21. A process as defined by claim 1 wherein said galioaluminosilicate
molecular sieve having the faujasite structure has the following
composition expressed in terms of oxide mole ratios in the anhydrous
state
wherein a equals 0.5 to 0.99 b equals 0.01 to 0.5 c equals 3
to 7 d is approximately 1.0 and a+b equals 1.0.
22. A process as defined by claim 1 wherein said crystallization
takes place in less than about 2 days.
23. A process as defined by claim 1 wherein the silica-to-alumina
mole ratio in said aluminosilicate hydrogel equals 8 to 12.
24. A process as defined by claim 23 wherein the silica-to-gallia
mole ratio in said galliosilicate solution equals 10 to 20.
25. A process as defined by claim 1 wherein said crystalline, gallioaluminosilicate
molecular sieve contains between about 10 and about 35 weight percent
alumina.
26. A process as defined by claim 1 wherein said crystallization
takes place in less than about 1 day.
27. A process as defined by claim 7 wherein said crystalline, gallioaluminosilicate
molecular sieve contains between about 10 and about 35 weight percent
alumina.
28. A process as defined by claim 7 wherein said crystallization
takes place in less than about 2 days.
Molecular sieve description
BACKGROUND OF THE INVENTION
This invention relates to crystalline molecular sieves containing
both aluminum and gallium, and is particularly concerned with a
method for synthesizing a crystalline gallioaluminosilicate molecular
sieve having the faujasite structure.
Zeolites are well known natural and synthetic molecular sieves
that can be defined as crystalline, three-dimensional aluminosilicates
consisting essentially of alumina and silica tetrahedra which interlock
to form discrete polyhedra. The polyhedra are interconnected to
form a framework which encloses cavities or voids interconnected
by channels or pores. The size of the cavities and pores will vary
depending on the framework structure of the particular zeolite.
Normally, the cavities are large enough to accommodate water molecules
and large cations which have considerable freedom of movement, thereby
permitting sorption, reversible dehydration and ion exchange. The
dimensions of the cavities and pores in a zeolite are limited to
a small number of values and can vary from structure to structure.
Thus, a particular zeolite is capable of sorbing molecules of certain
dimensions while rejecting those of dimensions larger than the pore
size associated with the zeolite structure. Because of this property
zeolites are commonly used as molecular sieves.
In addition to their molecular sieving properties, zeolites show
a pronounced selectivity toward polar molecules and molecules with
high quadrupole moments. This is due to the ionic nature of the
crystals which gives rise to a high nonuniform electric field within
the micropores of the zeolite. Molecules which can interact energetically
with this field, such as polar or quadrupolar molecules, are therefore
sorbed more strongly than nonpolar molecules. This selectivity toward
polar molecules is the unique property of zeolites which allows
them to be used as drying agents and selective sorbents.
In addition to their use as drying agents and selective sorbents,
zeolites are widely used as components of chemical conversion catalysts.
As found in nature or as synthesized, zeolites are typically inactive
because they lack acid sites. In general, acid sites are created
by subjecting the zeolite to an ion exchange with ammonium ions
followed by some type of thermal treatment which creates acid sites
by decomposing the ammonium ions into gaseous ammonia and protons.
Activated zeolites have been used in many types of chemical conversion
processes with the smaller pore zeolites being used to selectively
sorb and crack normal and moderately branched chain paraffins.
Because of the unique properties of zeolitic molecular sieves,
there have been many attempts at synthesizing new molecular sieves
by either substituting an element for the aluminum or silicon present
in zeolitic molecular sieves or adding another element in addition
to the aluminum and silicon. The term "zeolitic" as used
herein refers to molecular sieves whose frameworks are formed of
substantially only silicon and aluminum in tetrahedral coordination
with oxygen. One such class of new molecular sieves that has been
created is that in which a portion of the framework aluminum has
been replaced by gallium. Specifically, it has been reported in
U.S. Pat. No. 3431219 that gallioaluminosilicate molecular sieves
having the faujasite structure have been synthesized. The synthesis
process, as illustrated in Example 3 of the patent, involves the
separate preparation of a colloidal silica solution and a solution
comprised of a mixture of gallium hydroxide dissolved in aqueous
sodium hydroxide and sodium aluminate dissolved in water. According
to the example, the silica solution was added to the other solution
with rapid stirring and the resultant gel maintained at room temperature
overnight and then heated to 200.degree. F. Although some crystalline
material was present after 6 days, crystallization was not complete
until 12 days had past. Such long crystallization times are impractical,
and it is therefore clear that a simple process utilizing inexpensive
reactants to more rapidly produce gallioaluminosilicate molecular
sieves with the faujasite structure is desirable.
Accordingly, it is one of the objects of the present invention
to provide a relatively simple and rapid process for synthesizing
crystalline, gallioaluminosilicate molecular sieves having the faujasite
structure, which sieves may be useful in many types of chemical
conversion processes, particularly hydrocarbon conversion processes.
This and other objects of the invention will become more apparent
in view of the following description of the invention.
SUMMARY OF THE INVENTION
In accordance with the invention, it has now been found that a
crystalline, gallioaluminosilicate molecular sieve comprising silicon,
aluminum, gallium and oxygen and having the faujasite crystal structure
can be synthesized by mixing a source of alumina, a source of silica,
a source of sodium and water to form a hydrogel substantially free
of gallia in which the components have the following oxide mole
ratios:
After the above-described hydrogel is formed, it is mixed with
a galliosilicate solution substantially free of alumina prepared
by mixing a source of gallia, a source of silica, a source of sodium
and water. The mole ratio of Na.sub.2 O-to-Ga.sub.2 O.sub.3 in the
galliosilicate solution is sufficiently large to prevent gel formation,
or, if a gel does form, to facilitate dissolution of the gel upon
vigorous stirring. The components comprising the solution are typically
present in the following oxide mole ratios:
After the alumina-free solution is added to the gallia-free aluminosilicate
hydrogel, the mixture is crystallized, normally without substantial
agitation and at a temperature below about 250.degree. C., preferably
below 150.degree. C., to form a crystalline, gallioaluminosilicate
molecular sieve having the faujasite structure. This molecular sieve
typically has the composition, expressed in terms of oxide mole
ratios in the anhydrous state, of:
where a equals 0.5 to 0.99 b equals 0.01 to 0.5 c equals 2.0
to 10 d equals about 1.0 and a+b equals 1.0.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 in the drawing shows the X-ray powder diffraction pattern
of a zeolite with the faujasite structure;
FIG. 2 depicts the X-ray powder diffraction pattern of a molecular
sieve synthesized in accordance with the process of the invention
as exemplified in Example 1; and
FIG. 3 shows the X-ray powder diffraction pattern of the molecular
sieve synthesized in accordance with the process of Example 2.
DETAILED DESCRIPTION OF THE INVENTION
A crystalline, gallioaluminosilicate molecular sieve having the
faujasite structure is prepared by crystallizing a mixture of an
aluminosilicate hydrogel and a galliosilicate solution essentially
free of alumina and particulates. Both the hydrogel and the solution
are separately formed by mixing either a source of alumina or a
source of gallia, a source of silica, and a source of sodium with
water under conditions such that the various components react to
form, respectively, the desired hydrogel and the desired solution.
The crystallization is carried out in the absence of an organic
templating or directing agent. The gallioaluminosilicate molecular
sieve formed upon crystallization will normally contain between
about 10 weight percent and about 35 weight percent alumina, preferably
between about 15 and 25 weight percent, and between about 0.1 weight
percent and about 15 weight percent gallia, preferably between about
1.0 and 5.0 weight percent.
The silica used in forming the aluminosilicate hydrogel and galliosilicate
solution may be in the form of sodium silicate, silica hydrosols,
silica gels, silica salts, silicic acid sols, silicic acid gels,
aerosils, organic silica salts such as tetramethylammonium silicate
and methyltriethoxysilane, and reactive amorphous solid silicas.
The source of the silica can be in either the liquid or solid state.
Examples of reactive, amorphous solid silicas that may be used include
fumed silicas, chemically precipitated silicas, and precipitated
silica sols usually having a particle size of less than 1 micron
in diameter. The preferable sources of silica are sodium silicates
(water glass) and aqueous colloidal solutions of silica particles.
The alumina used to produce the aluminosilicate hydrogel may be
in the form of aluminum oxide with or without waters of hydration,
aluminum hydroxide, an inorganic aluminum salt such as aluminum
nitrate, sulfate, chloride or acetate, sodium aluminate and aluminum
alkoxydes. The use of sodium aluminate is normally preferred.
The source of sodium used in forming the aluminosilicate hydrogel
and the galliosilicate solution may be a sodium salt or sodium hydroxide.
It is possible for the source of sodium used to prepare the galliosilicate
solution to also be the source of gallia utilized to form the solution.
Sodium gallates are examples of materials which serve as a source
of both sodium and gallia.
The gallia used to produce the galliosilicate solution may be in
the form of gallium oxide, gallium hydroxide, an alkali metal gallate
or an inorganic gallium salt, such as gallium nitrate, gallium sulfate,
and gallium acetate. As mentioned above, the source of the gallia
may also be the source of sodium required to form the galliosilicate
solution. In fact, a preferred source of gallia is prepared by dissolving
gallium oxide in an aqueous solution of sodium hydroxide to form
sodium gallate which is then used as a component to form the galliosilicate
solution.
The aluminosilicate hydrogel used to form the mixture from which
a gallioaluminosilicate molecular sieve with the faujasite structure
is crystallized is normally prepared by first dissolving the source
of alumina in an aqueous solution of sodium hydroxide. The resulting
solution is then mixed with a source of silica to form a hydrogel
which is vigorously stirred. A sufficient amount of the alumina
source, the silica source, the sodium source and water is used so
that the resultant hydrogel contains the following oxide mole ratios
of components:
The galliosilicate solution that is added to the hydrogel to form
the crystallization mixture is substantially free of alumina and
dispersed particles and is typically prepared by dissolving a source
of gallia in aqueous sodium hydroxide and mixing the resulting solution
with a silica source. A sufficient amount of the gallia source,
the silica source, the sodium source and water is used so that the
resultant mixture contains the following oxide mole ratios of components:
Generally, a sufficient amount of the sodium source is used so
that the Na.sub.2 O/Ga.sub.2 O.sub.3 ratio is such that a gel is
not formed when the components are mixed together or, if a gel is
formed upon the mixing of the components, it can be forced into
solution by stirring at ambient temperature.
After the aluminosilicate hydrogel and the galliosilicate solution
have been separately prepared, a sufficient amount of the solution
is added to the hydrogel so that the resultant mixture, which remains
in a gel form, contains between about 1 and about 40 weight percent
of the solution, preferably between about 10 and about 30 weight
percent. Normally, the oxide mole ratio of components in the resultant
mixture will fall within the following ranges:
The mixture is then stirred at atmospheric pressure and preferably
at about ambient temperature for from about 1 hour to about 2 days,
preferably between about 1 hour and about 10 hours. After stirring,
the mixture is crystallized by heating in the absence of substantial
stirring or agitation for between about 1 day and 5 days, usually
in 3 days or less, at a temperature in the range between about 70.degree.
C. and 150.degree. C., preferably between about 90.degree. C. and
110.degree. C. The temperature is normally controlled within the
above ranges while avoiding substantial agitation in order to prevent
the formation of phase impurities. After the mixture has been crystallized,
the resulting slurry is passed to a filter, centrifuge or other
separation device to remove the excess reactants or mother liquor
from the crystallized molecular sieve. The crystals are then washed
with water and dried at a temperature between about 50.degree. C.
and about 200.degree. C. to remove surface water.
The dried crystals produced as described above will normally have
the following composition expressed in terms of oxide mole ratios
in the anhydrous state:
where a equals 0.5 to 0.99 b equals 0.01 to 0.5 c equals 2.0
to 10 preferably 3 to 7 d equals about 1.0 and a+b equals 1.0.
The X-ray powder diffraction pattern of the crystallized molecular
sieve will typically contain at least the d-spacings set forth in
Table 1 below.
TABLE 1 ______________________________________ Bragg Angle Interplanar
2-Theta d-spacings Relative Intensity (Degrees) (Angstroms) (100
.times. I/I.sub.o) ______________________________________ 5.9-6.4
14.967-13.799 80-100 15.4-15.9 5.7488-5.5691 30-70 23.3-24.0 3.8144-3.7047
30-80 26.7-27.4 3.3359-3.2522 20-50 31.0-31.8 2.8823-2.8139 30-70
33.7-34.4 2.6573-2.6069 5-30 ______________________________________
The X-ray powder diffraction data set forth in Table 1 is characteristic
of a molecular sieve having the faujasite structure. For comparison
purposes, the X-ray powder diffraction pattern of a synthetic zeolite
with the faujasite structure is shown in FIG. 1 and the corresponding
X-ray powder diffraction data are set forth in Table 2.
TABLE 2 ______________________________________ X-Ray-Powder Diffraction
Data for a Synthetic Zeolite with the Faujasite Structure Bragg
Angle Interplanar 2-Theta d-spacings Relative Intensity (Degrees)
(Angstroms) (100 .times. I/I.sub.o) ______________________________________
6.143 14.3764 100.0 10.077 8.7705 25.4 11.836 7.4707 18.2 14.434
6.1318 1.1 15.600 5.6759 52.3 18.638 4.7571 21.7 20.316 4.3677 33.6
21.110 4.2052 1.7 22.746 3.9063 10.5 23.595 3.7676 57.0 24.950 3.5660
3.7 25.734 3.4591 7.5 26.990 3.3009 37.2 27.720 3.2156 6.4 29.576
3.0179 14.3 30.695 2.9104 17.9 31.338 2.8521 44.6 32.397 2.7612
15.6 33.032 2.7096 4.4 34.035 2.6320 14.6 34.627 2.5884 7.4 35.582
2.5211 2.9 37.123 2.4199 1.6 37.822 2.3768 9.1 39.244 2.2939 1.4
40.503 2.2254 3.2 41.346 2.1819 5.7 41.860 2.1563 3.0 43.175 2.0936
5.4 43.971 2.0576 4.0 45.726 1.9826 1.8 47.096 1.9281 2.6 ______________________________________
The X-ray powder diffraction data set forth in Table 1 for the
crystallized gallioaluminosilicate produced in accordance with the
process of the invention are based on data obtained using a Siemens
D-500 X-ray diffractometer with graphite-crystal monochromatized
Cu-K alpha radiation. The peak heights I, and their position as
a function of 2-theta, where theta is the Bragg angle, were read
from the diffractometer output. From this output the relative intensities,
100.times.I/I.sub.o, where I.sub.o is the intensity of the strongest
peak, were read. The interplanar spacings, d, in Angstroms corresponding
to the recorded peaks were then calculated in accordance with standard
procedures. It will be understood that the peak heights and d-spacings
associated with the X-ray powder diffraction pattern of the gallioaluminosilicate
molecular sieve may vary somewhat depending on various factors,
e.g., heat treatment, unit cell composition, crystal size, and whether
the molecular sieve has been exchanged with hydrogen ions or metal
cations.
After the synthesized gallioaluminosilicate crystals have been
washed and dried, they are typically treated in order to render
them active for acid catalyzed reactions. This procedure normally
comprises exchanging the molecular sieve with ammonium ions, hydrogen
ions, polyvalent cations such as rare earth-containing cations,
magnesium cations or calcium cations, or a combination of ammonium
ions, hydrogen ions, and polyvalent cations, thereby lowering the
sodium content to below about 2.0 weight percent, preferably below
about 1.0 weight percent and most preferably below about 0.05 weight
percent, calculated as Na.sub.2 O. When reducing the sodium content
using an ammonium ion exchange technique, the molecular sieve is
typically slurried for 1 to 5 hours at a temperature above ambient
temperature but less than about 100.degree. C. in an aqueous solution
containing a dissolved ammonium salt, such as ammonium nitrate,
ammonium sulfate, ammonium chloride and the like. Ordinarily, to
achieve extremely low levels of sodium cations, the ion exchange
procedure will be repeated at least twice, and occasionally several
times. After the ammonium exchange or other treatment to reduce
alkali metal content, the molecular sieve is calcined in air at
a temperature between about 400.degree. C. and about 700.degree.
C., preferably between about 500.degree. C. and about 600.degree.
C., for between about 5 hours and about 15 hours. Calcination after
an ammonium exchange serves to decompose the ammonium cations into
ammonia, which is driven off during the calcination step, and thereby
produce the catalytically active hydrogen form of the gallioaluminosilicate
molecular sieve.
A crystalline, gallioaluminosilicate molecular sieve having the
faujasite structure produced in accordance with the process of the
invention may be used as a component of a catalyst for converting
hydrocarbons and other organic compounds into more valuable reaction
products by acid catalyzed reactions, such as alkylation, transalkylation,
dealkylation, isomerization, dehydrocyclization, dehydrogenation,
hydrogenation, cracking, hydrocracking, dewaxing, hydrodewaxing,
oligomerization, aromatization, alcohol conversion reactions, the
conversion of syngas to mixtures of hydrocarbons and the like. In
utilizing such a gallioaluminosilicate as a catalyst component in
conversion processes as described above, it will normally be combined
with a porous, amorphous, inorganic refractory oxide component,
or a precursor thereof, such as alumina, silica, titania, magnesia,
zirconia, beryllia, silica-alumina, silica-magnesia, silicatitania,
a dispersion of silica-alumina in gamma alumina, a clay such as
kaolin, hectorite, sepiolite or attapulgite, combinations of the
above and the like. The preferred porous, inorganic refractory oxide
component will depend upon the particular conversion process involved
and will be well known to those skilled in the art. Examples of
precursors that may be used include peptized alumina, alumina gel,
hydrated alumina, silica-alumina gels, Ziegler-derived aluminas
and silica sols. The exact amounts of crystalline gallioaluminosilicate
and porous, inorganic refractory oxide used in the catalyst will
again depend upon the particular conversion process in which the
catalyst is to be used.
It will be understood that, although the primary use of the catalyst
will be in hydrocarbon conversion processes to convert hydrocarbon
feedstocks into desirable reaction products, the catalyst can also
be used to convert feedstocks or organic compounds other than hydrocarbons
into desired reaction products. For example, the catalyst can be
used to convert alcohols into transportation fuels and to convert
gaseous mixtures of carbon monoxide and hydrogen into hydrocarbons.
Depending on the particular type of conversion process in which
the catalyst containing a gallioaluminosilicate molecular sieve
with the faujasite structure is to be used, it may be desirable
that the catalyst also contain a metal promoter or combination of
metal promoters selected from Group IB, Group IIB, Group IIIA, Group
IVA, Group VA, Group VIB, Group VIIB or Group VIII of the Periodic
Table of Elements. As used herein "Periodic Table of Elements"
refers to the version found in the inside front cover of the "Handbook
of Chemistry and Physics," 65th Edition, published in 1984
by the Chemical Rubber Company, Cleveland, Ohio. Specific metal
components which may be used as promoters include components of
copper, silver, zinc, aluminum, gallium, indium, thallium, lead,
tin, antimony, bismuth, chromium, molybdenum, tungsten, manganese,
iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum,
rhenium, thorium and the rare earths. These metal promoters may
be ion exchanged into the crystalline gallioaluminosilicate itself,
they may be incorporated into the mixture of the crystalline gallioaluminosilicate
and the porous, inorganic refractory oxide, or they may be added
by impregnation after the catalyst particles have been formed.
The catalyst is normally prepared by mulling a crystalline gallioaluminosilicate
molecular sieve produced in accordance with the process of the invention
in powder form with the porous, inorganic refractory oxide component.
If desired, a binder such as peptized Catapal alumina may be incorporated
into the mulling mixture, as also may one or more active promoter
metal precursors. After mulling, the mixture is extruded through
a die having openings of a cross sectional size and shape desired
in the final catalyst particles. For example, the die may have circular
openings to produce cylindrical extrudates, openings in the shape
of three-leaf clovers so as to produce an extrudate material similar
to that shown in FIGS. 8 and 8A of U.S. Pat. No. 4028227 the
disclosure of which is hereby incorporated by reference in its entirety,
or openings in the shape of four leaf clovers. Among preferred shapes
for the die openings are those that result in particles having surface-to-volume
ratios greater than about 100 reciprocal inches. If the die opening
is not circular in shape, it is normally desirable that the opening
be in a shape such that the surface-to-volume ratio of the extruded
particles is greater than that of a cylinder. After extrusion, the
catalyst particles are broken into lengths of from 1/16 to 1/2 inch
and calcined in air at a temperature of at least 750.degree. F.,
usually between about 800.degree. F. and about 1200.degree. F.,
and preferably in the range between about 900.degree. F. and 1050.degree.
F.
As mentioned previously, metal promoter components may be mulled,
either as a solid or liquid, with a gallioaluminosilicate prepared
in accordance with the process of the invention and the porous,
inorganic refractory oxide component or precursor thereof to form
the catalyst extrudates prior to the calcination step. Alternatively,
the metal promoter component or components may be added to the catalyst
by impregnation after the calcination step. The metal promoter component
or components may be impregnated into the calcined extrudates from
a liquid solution containing the desired metal promoter component
or components in dissolved form. In some cases, it may be desirable
to ion exchange the calcined extrudates with ammonium ions prior
to adding the metal promoter component or components. After the
calcined extrudates have been impregnated with the solution containing
the metal promoter component or components, the particles are dried
and calcined in air at a temperature normally ranging between about
800.degree. F. and about 1100.degree. F. to produce the finished
catalyst particles.
In addition to a crystalline, gallioaluminosilicate molecular sieve
having the faujasite structure, the catalyst may also contain other
molecular sieves such as aluminosilicates, borosilicates, aluminophosphates,
silicoaluminophosphates, naturally occurring zeolites, pillared
clays and delaminated clays. Suitable aluminosilicates for combining
with a crystalline gallioaluminosilicate include Y zeolites, ultrastable
Y zeolites, X zeolites, zeolite beta, zeolite L, faujasite and zeolite
omega. The actual molecular sieve used in combination with a crystalline
gallioaluminosilicate will depend upon the particular conversion
process in which the resultant catalyst is to be used. The molecular
sieve of choice is normally incorporated into the catalyst by mixing
the molecular sieve with a crystalline gallioaluminosilicate and
porous, inorganic refractory oxide prior to mulling and extrusion.
It is typically preferred to use catalysts containing a crystalline
gallioaluminosilicate molecular sieve synthesized in accordance
with the process of the invention as a cracking catalyst in the
absence of added hydrogen or in hydroconversion processes such as
hydrodenitrogenation, hydrodesulfurization, hydrocracking and isomerization.
When used in hydroconversion processes, the catalyst will normally
contain hydrogenation components comprising metals selected from
Group VIII and/or Group VIB of the Periodic Table of Elements. These
hydrogenation metal components are incorporated into the catalyst
extrudates either prior to or after extrusion. Examples of Group
VIII and Group VIB metal components that may be used include nickel,
cobalt, tungsten, molybdenum, palladium and platinum components.
In some cases, it may be desirable that the catalyst contain at
least one Group VIII metal component and at least one Group VIB
metal component. When this is the case, the preferred combination
is a nickel and/or cobalt component with a molybdenum and/or tungsten
component.
If the hydrogenation metal component consists essentially of one
or more noble metals such as platinum or palladium or compounds
thereof, it is generally desired that the finished catalyst particles
contain between about 0.05 and about 10 weight percent of the hydrogenation
metal component, preferably between about 0.10 weight percent and
about 3.0 weight percent, calculated as the metal. If on the other
hand, the hydrogenation metal component consists essentially of
one or more non-noble metals, such as nickel or nickel and tungsten
or compounds thereof, it is normally desired that the finished catalyst
particles contain between about 1.0 and about 40 weight percent
of the hydrogenation metal components, preferably between about
3 weight percent and about 30 weight percent, calculated as the
metal oxide.
Feedstocks that may be subjected to hydroconversion processes using
a catalyst containing a gallioaluminosilicate synthesized in accordance
with the process of the invention include mineral oils, synthetic
oils, such as shale oil, oil derived from tar sands and coal liquids,
and the like. Examples of appropriate feedstocks for hydroconversion
processes include straight run gas oils, vacuum gas oils and catalytic
cracker distillates. Preferred hydroconversion feedstocks include
gas oils and other hydrocarbon fractions having at least about 50
weight percent of their components boiling above about 700.degree.
F.
In general, the temperature at which the hydroconversion process
takes place is between about 450.degree. F. and about 850.degree.
F., preferably between about 600.degree. F. and about 800.degree.
F. The pressure will normally range between about 750 and about
3500 p.s.i.g., preferably between about 1000 and about 3000 p.s.i.g.
The liquid hourly space velocity (LHSV) is typically between about
0.3 and about 5.0 reciprocal hours, preferably between about 0.5
and about 3.0. The ratio of hydrogen gas to feedstock utilized will
usually range between about 1000 and about 10000 scf/bbl, preferably
between about 2000 and about 8000 scf/bbl as measured at 60.degree.
F. and one atmosphere.
The nature and objects of the invention are further illustrated
by the following examples, which are provided for illustrative purposes
only and not to limit the invention as defined by claims. The examples
demonstrate a simple and rapid method of synthesizing a crystalline
gallioaluminosilicate with the faujasite structure and illustrate
the importance of avoiding substantial agitation during crystallization.
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