Molecular sieve abstract
This invention relates to the synthesis of large pore composite
molecular sieves and to the synthetic large pore composite molecular
sieves so produced. The molecular sieves of the invention have the
same general utilties of the comparable molecular sieves of the
prior art but have been found to be superior catalysts and absorbents.
This invention relates to a hydrothermal synthesis of large pore
molecular sieves from nutrients, at least one of which contains
an amorphous framework-structure, and which framework-structure
is essentially retained in the synthetic molecular sieve. This invention
stems from a discovery that the intrinsic porosity characteristics
of a nutrient that possesses an amorphous cation oxide-framework
can be substantially retained in the final molecular sieve containing
product formed by a hydrothermal process by carefully controlling
the conditions under which the hydrothermal process is conducted.
For example, the invention contemplates retention of the particle
size in a final molecular sieve-containing product that corresponds
with that of an amorphous cation oxide-framework nutrient used in
its manufacture. This invention drives the selection of process
conditions to achieve one or more of macro and meso porosity ("large
pore composite porosity") in the final molecular sieve product
as a direct product of the hydrothermal reaction producing the molecular
sieve. The invention allows the production of a molecular sieve
that is in situ incorporated in the framework morphology of a solid
cation oxide-framework used in the molecular sieve's manufacture.
Molecular sieve claims
We claim:
1. A process for producing a molecular sieve comprising:
impregnating a cation oxide framework comprising a first cation
oxide with a liquid containing a second cation different than the
first cation, said liquid being free of a pore forming agent;
drying the impregnated cation oxide framework comprising the first
and second cations;
impregnating the cation oxide framework comprising the first and
second cations with a liquid, said liquid containing a pore forming
agent, wherein the amount of the liquid containing pore forming
agent added during the impregnating does not exceed the incipient
wetness point of the cation oxide framework; and
heating said impregnated cation oxide framework comprising the
first and second cations to produce a large pore composite porosity
molecular sieve.
2. The process of claim 1 wherein the first cation is silicon.
3. The process of claim 2 wherein the second cation is aluminum.
4. The process of claim 3 wherein the framework comprising a first
cation oxide is amorphous.
5. The process of claim 4 wherein the framework comprising the
first and second cations is calcined prior to impregnation with
the liquid containing the pore forming agent.
6. The process of claim 5 wherein the calcining is effected at
a temperature of from about 300.degree. C. to about 700.degree.
C.
7. The process of claim 6 wherein the molecular sieve is a beta
zeolite.
8. The process of claim 7 wherein the heating to produce the molecular
sieve is at a temperature of from about 75.degree. to about 350.degree.
C.
9. The process of claim 8 wherein the crystalline content of the
molecular sieve is at least 25 weight percent.
10. The process of claim 9 wherein the crystalline content is at
least 50 weight percent.
11. The process of claim 1 wherein the molecular sieve is a zeolite.
12. The process of claim 7 wherein the pore forming agent is an
amine.
13. The process of claim 7 wherein the pore forming agent is a
quaternary ammonium compound.
14. The process of claim 1 wherein the framework comprising the
first and second cations is calcined prior to impregnation with
the liquid containing the pore forming agent.
15. The process of claim 14 wherein the pore forming agent includes
a cation.
16. The process of claim 15 wherein the cation is selected from
the group consisting of alkali and alkaline earth metals.
17. The process of claim 14 wherein the calcining is effected at
a temperature of from 150.degree. C. to 1000.degree. C.
18. The process of claim 17 wherein the calcining is at a temperature
of from about 300.degree. C. to about 700.degree. C.
19. The process of claim 15 wherein the calcining is effected at
a temperature of from about 300.degree. C. to about 700.degree.
C.
20. The process of claim 19 wherein the first cation is silicon.
21. The process of claim 5 wherein the framework comprising the
first and second cations is dried prior to calcining.
22. The process of claim 5 wherein the framework comprising the
first and second cations is dried during the calcining.
23. The process of claim 1 wherein the molecular sieve retains
the structure of the cation oxide framework comprising the first
and second cations.
24. A process for producing a molecular sieve, comprising:
impregnating a previously produced dried cation oxide framework
with a liquid, said cation oxide framework comprising silicon and
aluminum and said liquid containing a pore forming agent, wherein
the amount of the liquid added during the impregnating does not
exceed the incipient wetness point of the cation oxide framework;
and
heating the impregnated cation oxide framework to produce a large
pore composite porosity molecular sieve.
25. The process of claim 24 wherein the framework that is impregnated
is a calcined amorphous framework.
26. The process of claim 25 wherein said calcination was effected
at a temperature of from about 300.degree. C. to about 700.degree.
C.
27. The process of claim 26 wherein the molecular sieve is a beta
zeolite.
28. The process of claim 27 wherein the crystalline content of
the molecular sieve is at least 25 weight percent.
29. The process of claim 28 wherein the pore forming agent is a
quaternary ammonium compound.
30. The process of claim 24 wherein the molecular sieve retains
the structure of the cation oxide framework.
Molecular sieve description
BRIEF DESCRIPTION OF THE INVENTION
A method that stems from a discovery that the intrinsic porosity
characteristics of a nutrient that possesses an amorphous cation
oxide-framework can be substantially retained in the final molecular
sieve containing product formed by a hydrothermal process by carefully
controlling the conditions under which the process is conducted.
This invention drives the selection of process conditions to achieve
one or more of macro and meso porosity in the final molecular sieve
product as a direct product of the hydrothermal reaction producing
the molecular sieve. The invention allows the production of a molecular
sieve that is incorporated in the framework morphology of a solid
cation oxide-framework used in molecular sieve's manufacture.
The invention is directed to a novel solid molecular sieve composition
that contains
a) a preformed porous geometric framework where the pores are one
or more of macro and meso pores, and
b) interconnected in situ formed crystalline molecular sieve particles
that
(i) contain micro pores and
(ii) are structural components of the framework.
BACKGROUND TO THE INVENTION
The definition of molecular sieve, according to Szostak, "Molecular
Sieves, Principles Of Synthesis And Identification," 1989
Van Nostrand Reinhold, New York, N.Y., at page 3 is --
"A molecular sieve framework is based on an extensive three-dimensional
network of oxygen ions containing generally tetrahedral-type sites.
In addition to the Si.sup.+4 and Al.sup.+3 that compositionally
define the zeolite molecular sieves, other cations also can occupy
these sites. These cations need not be isoelectronic with Si.sup.+4
and Al.sup.+3 but must have the ability to occupy framework sites.
Cations presently known to occupy these sites within molecular sieve
structures are --
(M.sup.+2 O.sub.2).sup.-2 where M is Be, Mg, Zn, Co, Fe, Mn
(M.sup.+3 O.sub.2).sup.-1 where M is Al, B, Ga, Fe, Cr
(M.sup.+4 O.sub.2).sup.0 where M is Si, Ge, Mn, Ti
((M.sup.+5 O.sub.2).sup.+1 where M is P."
The term molecular sieve encompasses the variety of structures
within the classification set forth in FIG. 1.1 of Szostak, supra,
page 2 which classification is incorporated by reference. Molecular
sieves come in two varieties, zeolitic molecular sieves ("ZMS")
and non-zeolitic molecular sieves ("NZMS"). Szostak (page
4) treats aluminosilicates generally to be ZMS provided there is
at least one aluminum ion per unit cell based on the bulk composition
of the sample. The remaining structures are recognized to be NZMS.
According to this characterization, the ZSM-5 structure is considered
a ZMS at silica/alumina less than 190 and NZMS above 190. This same
convention holds when ZMS's contain trace amounts of other elements
in the framework ion positions. (See Szostak, page 5 who considers
a crystalline structure a ZMS if the number of other cations in
the framework, other than aluminum and silicon, averages less than
one per unit cell, all others being a NZMS.)
Zeolitic molecular sieves are typically made from a source of silica
that is reacted with a source of aluminum, in the presence of materials
that insure significantly alkaline conditions, water and .sup.--
OH. The mix of the reactants may be called the reaction's nutrients.
Many of the reactions are conducted in the presence of an organic
template or crystal-directing agent, which induces a specific zeolite
structure that can not be formed in the absence of the organic template.
Most of the organic templates are bases, and many introduce hydroxyl
ions to the reaction system. The reaction involves a liquid gel
phase ("soup") in which rearrangements and transitions
occurs, such that a redistribution occurs between the alumina and
silica nutrients, and structural molecular identities corresponding
to specific zeolites or other molecular sieves are formed. It is
known that zeolites are not often formed above 350.degree. C., though
descriptions of higher temperature formation of certain molecular
sieves has been mentioned in the literature (see Szostak, supra,
page 52). Lower temperatures than about 100.degree. C. require extensive
crystallization time. As Szostak, supra, page 54 points out --
Upon mixing of the reagents on the synthesis of zeolite molecular
sieves, a gel generally is observed to form, which with time begins
to separate into two phases: a solid and a liquid. Visually, as
the crystallization progresses, the gel plus the forming crystals
increases in density and begins to settle to the bottom of the crystallization
vessel, as the forming zeolite crystals have a density greater than
that of the initial gel. Thus successful crystallization sometimes
can be suspected if a very dense, easily settling solid phase is
observed in the crystallization vessel when the crystallization
is terminated.
When the desired crystal structure is obtained, the molecular sieve
is brought to ambient temperatures and the crystallization process
is arrested. The product of the reaction is isolated typically as
a loose powder. The crystals that are formed in the powder are so
assembled in the structure as to form special micro pores and micro
pore openings of a kind that distinguishes the structure. The resulting
crystals are an assemblage of individual units the growth of which
may be small, medium or large, depending on the conditions employed
in the traditional method. The crystals may then, in the usual case,
be formed into composite structures that allow their use as, e.g.,
absorbents and catalysts.
A number of references describe processes for making ZMS by reacting
an amorphous precursor in the presence of a small amount of water
to form a dense interbonded mass. The amount of water is selected
to be less than that which is used in the aforementioned traditional
method but large enough to interbond the ZMS particles into dense
masses.
For example, Haden et al., U.S. Pat. No. 3065064 convert to
a ZMS, a dehydrated kaolin clay having a SiO.sub.2 /Al.sub.2 O.sub.3
mol ratio of about 2 in the presence of a "concentrated aqueous
solution of NaOH." The H.sub.2 O to Na.sub.2 O mol ratio in
the mixture is within the range of 4.5-11.5 "and being present
in an amount such that the Na.sub.2 O/SiO.sub.2 mol ratio in the
mixture is about 0.5. " According to Haden et al.:
". . . the alkali is then reacted with the alumina and/or
silica of the dehydrated aluminum silicate until substantially all
of the alkali is consumed, such reaction being carried out while
controlling the temperature of the mass below that at which water
will be evaporated from the mass at the pressure employed and in
the absence of an aqueous liquid phase external to and in contact
with the mass. The reaction product is a coherent mass of substantially
homogeneous amorphous composition and is the precursor of the desired
synthetic crystalline zeolite. The amorphous reaction product is
then aged without substantial dehydration thereof, preferably at
elevated temperature under autogenous pressure or greater, to crystallize
the material into the desired substantially homogeneous polycrystalline
zeolite of the empirical formula Na.sub.2 O.Al.sub.2 O.sub.3.2SiO.sub.2.4-5H.sub.2
O in the form of a hard coherent mass of essentially the same volume
as the original aluminum silicate-alkali mass. "
According to the patentee, the object of the process is to form
the ZMS into a "compact mass or masses" which is defined
as a "dense or substantially nonporous mass." The patentee
states,
"only such dense masses react to provide a sufficient number
of structural bridges between crystals to form the zeolite in the
desired form of hard crystalline aggregates occupying essentially
the same volume as the unreacted mass as opposed to the finely divided
or pulverulent masses inherently formed in carrying out prior art
methods for producing the synthetic crystalline zeolite A."
Miller, U.S. Pat. No. 5558851 patented Sep. 24 1996 relates
to shaped zeolite structures wherein the reactants, in making the
structures, are formed into a water-wet thick paste and crystallized
after forming into a shaped structure. According to Miller's process,
and as practiced by Haden et al., crystallization occurs without
the presence of an "external liquid phase.".sup.1 Needless
to say, Miller's process transforms the reactants into the typical
hydrothennally induced liquid phase reaction. According to Miller,
the zeolites in the shaped structures contain "very small crystallites."
Miller's use of low amounts of alkali metal should be expected to
generate smaller crystallites (See Szostak, supra, page 73). As
is the case with Haden et al., supra, Miller interbonds the ZMS
particles so as to form the dense mass structure described by Haden
et al.
According to Miller's example 16 (specifically at column 21 lines
1-20), a mixture of TPAOH, NaOH and water were combined with a mixture
of silica and sodium aluminate, and the combination was mixed for
3 hours. A paste was formed of the combination by the addition of
more water. Miller then combined the technique of Haden et al.,
supra, by the addition of kaolin clay, and he reduced the volatiles
level to 53 weight percent by continued mixing at 60.degree. C.
Miller then air-dried the mixture to form a powder of 48 weight
percent volatiles. According to Miller, "[t]he molar ratio
of H.sub.2 O/SiO.sub.2 at this point was about 2.5. " It is
assumed that the powder was an aggregation of pasted particles that
no longer exhibit the particulateness and porosity of the silica.
Miller placed the powder into a Teflon bottle and the bottle was
placed "in a stainless steel pressure vessel and heated at
140.degree. C. and autogenous pressure for two days." According
to Miller, the "resulting product was washed with water, dried
overnight in a vacuum oven at 120.degree. C., and calcined in air
for three hours at 593.degree. C." Miller states that "X-ray
diffraction analysis showed the product to be nearly 100% ZSM-5.
The average crystallite size by SEM was about 0.1 micron."
Ramesh B. Borade and Abraham Clearfield, ("Borade and Clearfield"),.sup.2
make a zeolite Beta in a 24 hour synthesis at 170.degree. C. from
an extremely dense system in which the weight ratio of solid, measured
as sodium aluminate and silica, to liquid, measured as tetraethylammoniumn
hydroxide and water, mixtures is 1:1.8. They found that the product
has comparable catalytic properties to samples prepared by previous
methods. According to the detail description of Borade and Clearfield,
the amount of the aforementioned liquid component "is just
sufficient to wet all the solid particles and in some cases (especially
at Si/Al ratio<10) the reaction mixture is in the form of small
lumps." According to the authors, the process uses "a
much smaller proportion of TEAOH and shorter reaction time as compared
to the usually synthetic methods." Lowering the proportion
of TEAOH allows the decrease in the amount of water content. "This
change increases the weight ratio of solid to liquid in the systems
from 1:9.1 to 1:1.8. The mole ratios of SiO.sub.2 /TEAOH increased
from 0.53 to 6 and H.sub.2 O/SiO.sub.2 decreased from 23 to 6.1.
"
The procedure employed by Borade and Clearfield is as follows:
"Sodium aluminate, TEAOCH and water were mixed and stirred
for about 15 minutes. Then, this solution was added to a highly
reactive fumed silica and stirred with a spatula for about 15 minutes.
Initially, the mixture appears to be a dry powder. As stirring continued
for about 2 hours the mixture turned into a very dense and thick
solid (solid: liquid .sup..about. 1:2), which was transferred into
a stainless-steel autoclave and heated at 443K and autogenous pressure
for 24 hours. The pH of the initial reaction mixture was in the
range 13.2-13.8 and after crystallization it was in the range 11.4-12.0.
After synthesis samples were dried at 120.degree. C. and then calcined
at 540.degree. C. for about 15 hours." According to the authors,
"[T]he marked reduction in the use of TEAOH in the present
method (2.5 versus 10-28 moles of TEAOH with reference to 1 mole
of Al.sup.2 O.sub.3), shorter crystallization time (24 hours versus
4-10 days) and increased productivity (per batch) should lead to
a lower synthesis cost of zeolite Beta. The product obtained also
has comparable catalytic properties at least with reference to the
cracking of hexane."
The methods of Haden et al., U.S. Pat. No. 3065064 Miller, U.S.
Pat. No.5558851 and Borade and Clearfield, take a common approach
to making ZMS, by reducing the amount of gelation of SiO.sub.2.
This is accomplished by the use of smaller amounts of water than
has been used in the traditional process for making ZMS. As a result,
Borade and Clearfield produce a very dense and thick solid, Miller
produces a paste that forms a dense and thick solid, and Haden et
al. produce a dense or substantially nonporous mass.
In effect, these authors have developed a process that depends
on surface gelation of the silica particles for ZMS formation. Surface
gelation occurs at the particle interior and exterior surfaces.
It allows the particles to become glued to each other by interfacial
wetting of one viscid exterior surface by another. It also affects
the interior pores by filling or collapsing pores thereby reducing
the particle's pore volume.
Surface gelation allows Haden et al. and Miller to make shaped
ZMS structures. However, such surface gelation as pointed out by
Haden et al. results in a relatively nonporous structure, meaning
that the macro and meso pores.sup.3 of the silica are eliminated
by the gelation and bonding that occur in their processes.
It is well known that molecular sieves are made from cation-oxide
containing materials, such as silica and alumina, which prior to
hydrothermal conversion contain macro and meso pores and a geometric
framework that surrounds and formns such pores. In the thermal conversion
of these porous materials, the framework is degraded and the framework
becomes part of a viscid (gelatinous) soup, no longer capable of
providing the macro and meso pore network. The typical product of
the typical hydrothermal conversion is a powdery precipitate.
Haden et al., U.S. Pat. No. 3065064 Miller, U.S. Pat. No. 5558851
and Borade and Clearfield, operate a "non-soup" hydrothermal
process designed to create an amount of surface gelation that essentially
eliminates the porosity inherent in the precursor cation-oxide containing
framework materials in order to form a paste and achieve increased
density.
There is described in the heterogeneous catalyst art a number of
processes for forming a catalyst. One method is characterized as
an impregnation of the catalyst support with liquid reagents that
deposit in the pores of the support. It is commonly known as an
impregnation process. The amount of liquid reagent deposited on
the support leaves an apparent incipient wet film. Those ingredients
invariably react on the surface of the support to form the catalyst.
The support is not changed by virtue of such treatment, and retains
its original porosity. In most cases, the support is not thought
to react with the liquid reagents. (See Stiles and Koch, Catalyst
Manufacture, Second Edition, 1995 published by Marcel Dekker, Inc.,
New York, N.Y. 10016.)
There is no process known in the art that causes conversion of
conventional molecular sieve forming nutrients that retains macro
and meso porosity characteristics of a geometric framework cation-oxide
containing nutrient. It would be desirable to produce molecular
sieves that possess a framework morphology characteristic of at
least one of cation oxide containing nutrients in the reaction.
It would be desirable to have a reaction of the typical nutrients
in the formation of a molecular sieve that retains the framework
morphology characteristic of at least one cation oxide containing
nutrients in the reaction.
THE INVENTION
This invention relates to the synthesis of large pore composite
molecular sieves and to the synthetic large pore (as defined herein)
composite molecular sieves so produced. The molecular sieves of
the invention have the same general utilities of the comparable
molecular sieves of the prior art. However, the large pore composite
molecular sieves of the invention have been found to be superior
catalysts and absorbents to the compositionally and structurally
comparable molecular sieves of the prior art. This superiority is
seen to result from the large pore composite feature of the composite
molecular sieves obtained by the process of the invention.
This invention relates to a hydrothermal synthesis of composite
molecular sieves from nutrients, at least one of which contains
an amorphous framework-structure, and which framework-structure
is essentially retained in the synthetic molecular sieve. This invention
stems from a discovery that the intrinsic porosity characteristics
of a nutrient that possesses an amorphous cation oxide-framework
can be substantially retained in the final molecular sieve containing
product formed by a hydrothermal process by carefully controlling
the conditions under which the hydrothermal process is conducted.
For example, the invention contemplates retention of the particle
size in a final molecular sieve-containing product that corresponds
with that of an amorphous cation oxide-framework nutrient used in
its manufacture. The invention further contemplates hydrothermal
impregnation of an amorphous cation oxide-framework having an average
particle size of about 0.1 microns to about 5 millimeters with aqueous
containing nutrients to produce a molecular sieve-containing structure
therefrom that has essentially the same average particle size. This
invention drives the selection of process conditions to achieve
one or more of macro and meso porosity ("large pore composite
porosity") in the final molecular sieve product as a direct
product of the hydrothermal reaction producing the molecular sieve.
The invention allows the production of a molecular sieve that is
in situ incorporated in the framework morphology of a solid cation
oxide-framework used in the molecular sieve's manufacture.
This invention relates to the hydrothermal treatment of nutrients
used in the manufacture of molecular sieves where at least one of
the nutrients possesses geometric frameworks that contains one or
more of macro and meso porosity (the "framework porosity")
within it. According to this invention, hydrothermal conditions
are selected to preserve at least 25 volume percent of the framework
porosity, preferably 50 volume percent of the framework porosity,
while at the same time effecting reaction of the nutrients such
that a molecular sieve is formed within the boundaries of the framework-structures.
The process of this invention effects intermolecular reactions of
the nutrients such that a molecular sieve of the type desired is
formed while at the same time substantially preserving the geometric
framework-structure or morphology of at least one of the nutrients
possessing said geometric framework. The process of this invention
uses a nutrient with a porous framework-structure. The process of
this invention effects at least partial reaction and transformation
of the framework nutrient without destroying the porous nature of
the framework.
In another aspect of this invention, the process of the invention
involves the incremental reaction of impregnated nutrients within
a cation oxide geometric framework that is suitable for forming
a molecular sieve therein. The added nutrients react with the cation
oxide geometric framework in such a way that it allows one to produce
a crystalline molecular sieve within such framework. In this embodiment,
the framework-structure is impregnated by the incipient wetness
method with the additional nutrients, in one or more steps to produce
a uniform distribution within the structure. It is believed that
the added nutrients react within the framework-structure in such
a way that they meter the rate at which solubilization occurs during
the induction period to molecular sieve growth and/or during the
molecilar sieve crystallization process. This allows for an ordered
reaction of the added nutrients with the framework-structure nutrient,
and this insures and promotes high yields of molecular sieve in
the framework-structure while retaining the large composite pores
provided by the cation oxide geometric framework.
The original framework-structure is amorphous, and the final framework-structure
after crystallization contains a substantial crystalline content,
typically at least 15 weight percent, preferably at least 25 weight
percent, more preferably at least 40 weight percent and most preferably
at least 50 weight percent, basis weight of the molecular sieve.
The final framework-structure may contain from 75 to 100 weight
percent crystalline molecular sieves, basis weight of the molecular
sieve.
This invention relates to a "dry" process for the making
of a molecular sieve by impregnating a solid cation oxide-framework-structure
with other nutrients suitable for a hydrothermal reaction between
the other nutrients and the solid cation oxide-framework-structure,
to form an impregnated pastefree composition. Then the impregnated
pastefree composition is subjected to conditions of temperature
and pressure to effect a hydrothermal reaction and convert the nutrients
of the reaction into a crystalline molecular sieve that possesses
the morphologic characteristics of the solid cation oxide-framework-structure.
The method of this invention for making a molecular sieve comprises
a) crystallizing at an elevated temperature,
i) a solid amorphous cation oxide-containing framework material
possessing framework porosity and physical boundaries,
ii) optionally in the presence of a pore forming material (template),
iii) in the absence of an amount of free water (as contrasted with
bound water) that is sufficient to cause substantial surface gelation,
and
b) transforming the solid macro and meso pore-containing amorphous
cation oxide-containing framework material into a solid molecular
sieve-containing product having the physical boundaries and morphology
of the solid pore-containing amorphous cation oxide-containing framework
material and a framework porosity similar to the framework porosity
of the amorphous cation oxide-containing framework material.
Specifically, the invention relates to a method for making a molecular
sieve, such as a zeolite, by crystallizing into a molecular sieve,
solid shaped amorphous silica framework materials ("solid material")
possessing a level of framework porosity, by heating the solid materials
in the presence of
(a) an aluminum containing component residing within the pores
of the solid material and
(b) a small quantity of water that contains, as needed, a micro
pore forming component, sufficient to crystallize the silica and
transform a significant portion of the solid material into a molecular
sieve,
1. without significantly changing the shape of the solid materials
and
2. without causing substantial surface gelation of the solid materials
that causes interbonding of the solid materials to occur.
The invention is directed to a novel solid molecular sieve composition
that contains
ii) a preformed large pore geometric framework-structure, and
iii) crystalline molecular sieve particles that contain micro pores
therein occupying structural components of the framework-structure.
DETAILED DESCRIPTION OF THE INVENTION
In the description of the invention, the effects of "surface
gelation" distinguish the prior art from this invention. In
the case of the prior art, surface gelation of the cation oxide-framework
causes loss of large pore composite porosity in the resulting molecular
sieve containing structures and that affects their performance capability.
In the practice of this invention, impregnation of a large pore
cation oxide keeps surface gelation to a minimum and there is minimal
loss of large pore composite porosity of the cation oxide-framework.
As a result, the molecular sieves of the invention are more active
catalysts and better absorbents than comparable molecular sieve
containing structures.
The invention relates to novel molecular sieve containing structures
and processes for making the structures. The molecular sieves of
the invention cover the wide variety of synthetic ZMS's and NZMS's
known in the art, each embodied within a framework-structure possessing
framework meso and/or macro, i.e., large pore composite porosity.
The process of the invention meters the interreactions of the molecular
sieve nutrients, at least one of which is amorphous framework-structure,
and through such metering, one can control surface gelation, cation
transitions, molecular sieve crystal size, and structural integrity
within such framework-structure. For example, the process of the
invention limits the amount of liquid in the hydrothermal reaction
such that there is very little to no surface gelation visible to
the naked eye. In other words, the reaction appears to be "dry"
because the liquid provided to the reaction wets the interior voids
of the amorphous framework nutrient. It is believed that the chemical
reactions occurring within the amorphous framework-structure predominantly
occur within the pores of the amorphous framework-structure. However,
the nature of these reactions is such that the porosity of the amorphous
framework-structure is essentially retained. If the amount of liquid,
in any such case, were to destroy the interior voids of the framework-structure
during hydrothermal reaction, then the amount of liquid is probably
too great for the objectives of this invention, and should be reduced
in order to preserve such porosity and framework-structure. It is
believed that the conversion of a amorphous cation oxide-framework-structure
to a molecular sieve containing structure is a phase transition
involving either a solid-solid transformation (see R. Szostak, supra,
page 190) or a viscid gel surface reaction that creates nuclei crystals
which grow to the molecular sieve crystals. The reaction is believed
to advance from the interior voids of the particle by a phase transition
of the surface of the particle structure and subsequently proceeds
to consume the particle throughout the structure as crystallization
progresses substantially uniformly therein.
This "dry" process for the making a molecular sieve involves
impregnating a solid cation oxide-framework-structure with other
nutrients such as water and a micro pore forming agent (e.g., an
organic templating agent and/or a metal (e.g., an alkali or alkaline
earth metal base)) without forming a paste and without destroying
the structure of the cation-oxide framework. The impregnation is
suitable for a paste-free hydrothermal reaction between the other
nutrients and the solid cation oxide-framework-structure. The impregnated
paste-free composition is subjected to conditions of temperature
and pressure to effect a surface hydrothermal reaction and convert
the nutrients of the reaction into a crystalline molecular sieve
that possesses the morphologic characteristics of the solid cation
oxide-framework-structure.
The "dry" reaction between the molecular sieve nutrients
occurs at the interior surfaces of the amorphous framework-providing
nutrient. Consequently, the amorphous framework-providing nutrient
is maintained dry thereby preserving the structural integrity of
the framework-structure of one of the ingredients. A dry reaction,
as used herein, means that the amount of surface gel formation is
insufficient to cause destruction of framework porosity of a framework
precursor, such as particles of silica, alumina, aluminosilicate,
titanium oxide, zirconium oxide, gallium oxide, arsenic oxide, germanium
oxide, metal phosphate, and the like. For example, if the amorphous
framework-providing nutrient were a free-flowing particle, it would
remain free flowing after impregnation by the other nutrients used
in the hydrothermal reaction and before the hydrothermal reaction.
However, it is contemplated according to the invention that individual
framework-structures may be interbonded prior to the hydrothermal
reaction and in many such cases, the interbonding creates macro
pores within the interbonded structure. For example, porous framework
material can be subjected to the hydrothermal conditions of reaction
and can undergo subtle surface gelation to structural points on
the exterior of the framework. Such surface gelation causes bonding
with adjacent framework-structures, and the interbonding typically
creates additional porosity, typically macro pores in the aggregated
structure. This bonding results in clustering and aggregations of
the molecular sieve containing framework-structures. Thus the amorphous
framework-structure that one may use in making the molecular sieves
of the invention may be particulate structures, and any bonded amorphous
framework-structure that contains porosity within which the dry
process can be conducted. The invention can be carried out with
small, medium and large size porous particles and any porous macrostructure
of such particles, including monolithic and joined monolithic structures.
Such an interbonded structure may then be subjected to hydrothermal
conditions of reaction in the presence of the correct nutrients
to cause the formation of molecular sieve crystals therein without
destroying the porosity and shape of the structure.
A significant embodiment of this invention involves the process
of making small crystalline molecular sieve particles that are of
a size amenable to extrusion and other molding processes into catalyst
structures. According to this process, cation oxide particles such
as silica, alumina, aluminosilicate, titanium oxide, zirconium oxide,
gallium oxide, arsenic oxide, germanium oxide, metal phosphate,
and the like, are committed to a smaller size porous particle than
the ultimate molecular sieve composite particle size. These smaller
particles are composited by conventional means to larger uniform
large porecontaining particles, e.g., having a mean average particle
size of about 5 mm, suitable for making catalysts. Then the composited
particles are subjected to hydrothermal reaction conditions according
to the invention to make a molecular sieve-containing product that
is ideal for catalysts in reactions that molecular sieves are conventionally
employed.
The selection of process conditions in the practice of this invention
is dependent upon the proportion of nutrients, especially the amount
of liquid in the nutrient mixture and the absorptive properties
of the amorphous cation oxide-framework-structure. For example,
the amount of water should be insufficient to cause pore elimination
and full densification of the framework-structure. The amount of
water should be insufficient to cause the formation of a paste from
the nutrients. The absorptive properties should be sufficient to
assure a dry reaction, as defined above. In most instances, the
amorphous framework-structure is subjected to conditions sufficient
to either maintain a low bound water content in the structure or
to sufficiently dry the amorphous framework-structure to achieve
a low bound water content. This is achieved by calcining the amorphous
framework-structure at a temperature and for a period of time to
remove excess bound water from the framework-structure. Typically,
calcination is effected at a temperature, at normal conditions,
of at least 150.degree. C. to about 1000.degree. C., or higher,
until the desired water content is achieved. Lower temperatures
result in longer calcination times and higher temperatures result
in shorter calcination times. The desired bound water content of
the amorphous framework-structure is dependent on the amount of
molecular sieve crystal development one desires in the final product
and the amount of water that it is desirable to add in the process.
The more water that one desires to add to the amorphous framework-structure
the less bound water one will tolerate in the amorphous framework-structure.
There is no clear limit on the amount of water that is tolerated
in the amorphous framework-structure and is useable in the hydrothermal
process other than the limitation that the amount should be such
as to provide for a dry reaction, as defined above. For example,
the amount of water that can be used to effect the dry reaction
might, in the presence of different nutrients, cause the formation
of a paste or a soup because of the amount of water that is provided
by the nutrients. Generally, the water content of the nutrients
is not mentioned or adequately controlled by the prior art.
In addition, the hydrothermal reaction should be carried out in
a sealed reaction vessel, typically at autogenous pressure, at moderate
temperatures, such as from about 25.degree. C. to about 500.degree.
C., preferably from about 75.degree. C. to about 350.degree. C.
and more preferably from about 100.degree. C. to about 250.degree.
C. The reaction has been most effectively carried out at temperatures
of about 150.degree. C. Contrary to the conventional "soup"
hydrothermal reaction, the process of the invention does not generate
a liquid or paste phase that is separable from the solid crystal
phase. Any liquid or paste phase is to be avoided in carrying the
impregnation process of the invention. After the hydrothermal reaction
has been carried out, typically within 2 to 130 hours, the solid
reaction product containing the framework-structure of a framework
nutrient of the reaction may be used as such, or calcined to generate
desired properties in the final product. That calcination may range
from about 150.degree. C. to about 1000.degree. C., preferably from
about 300.degree. C. to about 700.degree. C., and most preferably,
from 400.degree. C. to about 650.degree. C. The resulting molecular
sieve may then be used without any further processing, such as water
washing and filtering. However, water washing and filtration may
be employed if the cleanliness of the product dictates that such
treatments are desirable.
The framework precursor to the framework-structure of the molecular
sieve of the invention, may be any one of a variety of cation oxide
containing nutrients used in making molecular sieves. It may be
a silica, an alumina, a titanium oxide, a zirconium oxide, a gallium
oxide, an arsenic oxide, a germanium oxide, a metal phosphate, and
the like. Such framework-structure, as pointed out above, may be
small to large particles; aggregates of particles, fused particles,
extruded particles, molded particles, sheets of bonded particles,
monolithic fused particles, and the like, provided there is a porous
framework inherent in such structures.
A preferred amorphous framework-structure nutrient for use in the
process of the invention is silica, typically containing a low water
content. Most desirably, the silica is a synthetic material. Any
process may be used to form such silica so long as the silica contains
large pores, as defined herein. For example, the silica may be formed
by precipitation from a solution, by filming silica forming materials,
and the like processes. A very desirable framework-structure is
silica, typically a pure silica (i.e., it does not contain any other
cation oxide component), that has been reacted with a solvent soluble
aluminum source incorporated by impregnation up to incipient wetness
of the silica, without destroying the amorphous framework-structure
of the silica, allows on heating the formation of an aluminum silicate
therefrom. It is believed that such ingestion of aluminum into the
silica framework, aids in the subsequent dry hydrothermal processing
of nutrients to form the molecular sieves of the invention.
Suitable solvent soluble aluminum sources include alkali metal
(e.g., Li, Na, K, Rb, Cs) and alkaline earth metal (e.g., Be, Mg,
Ca, Sr, Ba) salts of aluminum hydroxides and aluminas, aluminum
salts of inorganic and organic acids, such as aluminum nitrate,
aluminum sulfate, aluminum chloride, aluminum phosphate, aluminum
monoacetate, aluminum diacetate, aluminum triacetate, aluminum monocitrate,
aluminum dicitrate, aluminum tricitrate, and mono, di, and tri alkyl
(e.g., C.sub.1 -C.sub.8) esters of aluminum hydroxide. The reaction
is typically carried out by forming a solvent solution or liquid
dispersion of the solvent soluble aluminum source and mixing it
with the silica framework-structure up to incipient wetness of the
silica framework-structure, followed by heating sufficiently to
effect transformation of the aluminum by reaction with the silica
surface and/or reaction with the silica bulk itself The reaction
conditions are essentially the same conditions as the hydrothermal
reaction used in forming the molecular sieve except that a micropore-forming
agent is not present in the reaction. The solvent used in the reaction
is typically water, though organic solvents such as alcohols, organic
acids, polyols, and the like, may be employed instead. The amount
of solvent soluble aluminum incorporated into the amorphous framework-structure
is dependent on the amount of aluminum desired in the molecular
sieve structure of the invention. Generally, the impregnation up
to incipient wetness of the silica with the aluminum source in the
solvent takes up to about 1 to 2 hours.
After the Al incorporation reaction has been carried out, typically
within 2 to 130 hours, the solid reaction product containing the
framework-structure of a framework nutrient of the reaction may
be used as such, or calcined to generate desired properties in the
final product. That calcination may range from about 150.degree.
C. to about 1000.degree. C., preferably from about 300.degree. C.
to about 700.degree. C., and most preferably, from 400.degree. C.
to about 650.degree. C. The resulting molecular sieve may then be
used without any further processing, such as water washing and filtering.
Templates for the hydrothermal reaction may be any of those known
in the art for controlling molecular sieve micro porosity, and influencing
the reaction to the desired molecular sieve crystals. The template
is generally characterized as an ion or neutral species which upon
its addition to the reaction mixture, crystallization is induced
of a specific zeolite structure that could not be formed in the
absence of the agent. Inorganic cations acting as counterions also
are dominant in determining which zeolite structure is obtained.
It is known that the cations can influence crystal morphology, crystallinity,
and yield. (See Szostak, supra, page 73) It has been shown that
such inorganic cations can influence crystal size. Suitable inorganic
cations are the alkali metals (Li, Na, K, Rb, Cs), the alkaline
earth metals (Be, Mg, Ca, Sr, Ba), the transition metals (Ti, Zr,
Hf, V, Nb, Ra, Cr, Mo, W, Mn, Tc, Re, Fe, Ru, As, Co, Rh, Ir, Ni,
Pd, Pt, Cu, Ag, Au, Zn, Cd, Hg) , and the like. In general the templating
agent may be an organic compound that contain elements of Group
VA of the periodic Table of Elements, particularly nitrogen, phosphorus,
arsenic and antimony, preferably N or P and most preferably N. The
compounds also contain at least one alkylene, alkyl or aryl group
having from 1 to 8 carbon atoms. Particularly preferred nitrogen-containing
compounds for use as templating agents are the amines and quaternary
ammonium compounds, the latter being represented generally by the
formula R.sub.4 N.sup.+ wherein each R is an alkyl or aryl group
containing from 1 to 8 carbon atoms. Polymeric quaternary ammonium
salts such as [(C.sub.14 H.sub.32 N.sub.2)(OH).sub.2 ].sub.x wherein
"x" has a value of at least 2 are also suitably employed.
Both mono-, di- and triamines are advantageously utilized, either
alone or in combination with a quaternary ammonium compound or other
templating compound. Mixtures of two or more templating agents can
either produce mixtures of the desired molecular sieve or the more
strongly directing templating species may control the course of
the reaction with the other templating species serving primraily
to establish the pH conditions of the reaction gel. Illustrative
organic templating cations are the following: tetramethylamonium
("TMA"), tetraethylammonium ("TEA"), tetra-n-propylammonium
("TPA"), tetra-isopropylanmionium, tetrabutylammonium
ions, di-n-propylamine, di-n-butylamine, tri-n-propylantine, triethylamine,
tributylamine, triethanolamine, quinuclidine ("Q"), methyl
quinuclidine hydroxide, cyclohexylamine, neopentylamines, N,N-dimethylbenzylamine,
N-N-dimethylethanolamine, di-n-pentylamine, isopropylamine, t-butylamine,
ethylenediamine; hexamethylenediamine, pyrrolidine; and 2-imidazolidone,
piperidine, 2-methylpyridine, N,N'-dimethylpiperazine, N-methyldiethanolamine,
N-methylethanolamine, N-methylpiperidine, 3-methylpiperidine, N-methylcyclohexylamine,
3-methylpyridine, 4-methylpyridine, diethylpiperidinium ("DEPP"),
trimethylbenzylammonium ("TMBA"), tetramethylphosphonium
("TMP"), 5-azoniaspiro(44)nonane or bispyrrolidinium
("BP"), (2-hydroxyethyl)trimethylammonium ("choline"),
14-dimethyl-14-diazoniabicyclo(222)octane ("DDO"),
14-diazoniabicyclo(222)octane ("DO" or "DABCO"),
N,N'-dimethyl-4-diazabicyclo (222) octane ion. It is well understood
by the art that every templating agent will direct the formation
of every species of molecular sieve, i.e., a single templating agent
can, with proper manipulation of the reaction conditions, direct
the formation of several molecular sieve compositions, and a given
molecular sieve composition can be produced using several different
templating agents.
The variety of molecular sieve covered by this invention includes
all of the synthetic molecular sieves. The invention embraces all
molecular sieves that can be made by chemical synthesis. This includes
such ZMS as the faujasite (Types X and Y), mordenite, cancrinite,
gmelinite, Type L, mazzite, offretite, omega, ZSM-12 beta, ZSM-5
and silicalite, ZSM-11 dachiardite, epistilbite, ferrierite, laumontite,
stilbite, ZSM-23 theta-1 and ZSM-22 Eu-1 and ZSM-50 ZSM-48 and
Eu-2 Type A and ZK-5 bikitaite, brewsterite, chabazite, TMA-E
and AB, edingtonite, erionite, gismondine, heulandite, levyne, merlinoite,
natrolite, phillipsite, paulingite, rho, thomsonite, yugawaralite,
and the like. It also includes the variety of NZMS's that have been
discovered such as the aluminophosphate molecular sieves, whose
acronyms are set forth in the following table:
______________________________________ Cations Acronym ______________________________________
Al, P AlPO.sub.4 Si, Al, P SAPO Me, Al, P MeAPO Fe, Al, P FAPO Mg,
Al, P MAPO Mn, Al, P MnAPO Co, Al, P CoAPO Zn, Al, P ZAPO Me, Al,
P, Si MeAPSO Fe, Al, P, Si FAPSOA Mg, Al, P, Si MAPSO Mn, Al, P,
Si CoAPSO Co, Al, P, Si CoAPSO Zn, Al, P, Si ZAPSO Other Elements:
El, Al, P ElAPO Al, Al, P, Si AlAPSO ______________________________________
See Szostak, supra, page 211
A listing of such NZMS can be found in U.S. Pat. No. 4440871
to Lok et al., and U.S. Pat. No. 4791083 to Pellet et al., and
such listing, and citations of patents and applications where the
manufacture of such NZMS can be found, are incorporated herein by
reference. A variety of non-alunminosilicate molecular sieves are
characterized by Szostak, supra, at table 4.1 (page 209), which
is reported below for convenience, and such non-aluminosiLicate
molecular sieves are incorporated herein by reference.
Some metallosilicate molecular sieves reported in the patent literature
and their known zeolite structure type:
__________________________________________________________________________
ASSIGNEE COMPOSITION (NAME) STRUCTURE PATENT NO. __________________________________________________________________________
AIST* iron silicate ZSM-5 Japan 110 421 Amoco Borosilicate (AMS-1B)
ZSM-5 U.S. Pat. No. 4269813 Chromosilicate (AMS-1Cr) ZSM-5 U.S.
Pat. No. 4299808 Aristech Magnesium silicate ZSM-5 U.S. Pat. No.
4623530 BASF Arsenic silicate ZSM-5 Germany 2 830 830 Chromosilicate
ZSM-5 Germany 2 831 630 Iron silicate ZSM-5 Germany 2 831 611 Niobium-aluminosilicate
ZSM-5 EP 0 089 574 Niobium-borosilicate ZSM-5 EP 0 089 574 Vanadium
silicate ZSM-5 Germany 2 831 631 Borosilicate (ZBH) Pentasil EP
0 077 946 Metallosilicate (Al, B, Ga, Ge) ZSM-5 EP 0 046 504 Bayer
Zinc silicate -- EP 0 071 136 BP Gallosilicate (Ga-theta-1) Theta-1
EP 0 106 478 Gallosilicate Analcite UK 2 102 779 Gallosilicate ZSM-5
PCT W 04/03879 Gallosilicate ZSM-39 UK 2 144 727 Union Carbide (now
UOP) iron silicate (FeSO-35) Levynite EP 0 115 031 Iron silicate
(FeSO-38) Mordenite EP 0 108 271 Chevron Chromosilicate (CZM) ZSM-5
Belgium 884 871 CRIQ** Titanoborosilicate (ZMQ-TB) ZSM-5 EP 0 104
107 Ironborosilicate ZSM-5 EP 0 148 038 Hoechst Boro-aluminosilicate)
-- EP 0 073 482 Gallium/indium silicate ZSM-34 EP 0 074 651 Gallium/indium
silicate -- EP 0 074 652 Zirconium/hafnium silicate -- EP 0 094
023 Titanosilicate -- EP 0 094 024 Huls Metallosilicates (transition
metals) -- EP 0 072 054 Idemitsu Borosilicate -- Japan O7 817 Borosilicate
-- Japan O7 821 Mitsubishi Metallosilicates (transitions metals)
-- Japan O7 820 Metallosilicates (Ni, W, Cr, -- EP 070 757 Fe, Ti,
Mo) Metallosilicates (transition metals) -- Japan O7 821 Metallosilicates
(transition metals) -- Japan 11 818 Mobil Metallosilicate (Al, Cr,
Fe, La) Beta EP 0 064 328 Iron/chrmoium silicates ZSM-12 EP 013
630 Iron/chromium silicates ZSM-11 EP 014 059 National Distillers
Borosilicates (USI-10B) -- U.S. Pat. No. 4423020 Nat. Res. Dev.
Metallosilicates (Zn, Sn, Ti) A, X EP 027 736 Shell iron silicate
ZSM-5 France 2 403 975 Cobalt silicate ZSM-5 EP 0 061 799 Shin Nenryoyu
Kaiha Metallosilicate (transition metals) -- Japan 196 719 Metallosilicates
(pentaval, met.) -- Japan 185 224 Bismuth silicate -- Japan 195
185 Metallosilicates (Zr, Cs, B, Y, Ga) -- Japan 185 225 Snamprogetti
Borosilicate (Boralite A) Nu-1 Italy 22 638 Borosilicate (Boralite
B) Beta Italy 22 638 Borosilicate (Boralite C) ZSM-5 Italy 22 638
Borosilicate (Boralite D) ZSM-11 Italy 22 638 Borosilicate (Boralite
E) -- Germany 3 316 488 Titanosilicate (TS-1) ZSM-5 U.S. Pat. No.
4410501 Metallosilicate (V, Be, Zn, Ti) ZSM-5 ZSM-11 Belgium 877
205 Union Molybdosilicate -- U.S. Pat. No. 4388224 __________________________________________________________________________
*Agency of industrial Science and Technology. **Center for industrial
Research of Quebec.
Szostak, supra, pages 51 to 132 inclusive, which is incorporated
herein by reference, describes in great detail the hydrothermal
process for making ZMS, and at pages 205 to 281 inclusive, which
is also incorporated herein by reference, describes in great detail
the hydrothermal processes for making the various NZMS's. The process
of this invention, which makes new ZMS and NZMS structures, draws
upon those descriptions developed in the prior art, but distinguishes
from the prior art in the manner by which the hydrothermal process
is carried out. The fundamental difference from the prior art is
that the process of this invention limits the hydrothermal reaction
conditions within the cation oxide amorphous framework-stnrcture
so that the process is dry, as characterized above. This means that
the various conditions used in the prior art can be employed in
the practice of this invention with the modification that the reaction
be controlled to operate as a dry reaction. This also means that
the rate at which water is incorporated in making the molecular
sieve is controlled to assure that dry conditions prevail. In some
cases, water is incrementally fed with or without other nutrients
to the amorphous framework-structure, and/or water with or without
other nutrients is provided to the amorphous framework-structure,
to a state of incipient wetness, and after digestion, more water
is similarly added. In this way the degree of conversion of the
amorphous framework-structure to molecular sieve is readily controllable.
Surprisingly, such procedures result in faster reactions and quicker
conversion of amorphous framework-structures to molecular sieve.
In some reactions, a limited amount of routine experimentation such
as reordering addition of nutrients and temperature condition for
crystal growth will be necessary to make a selected ZMS or NZMS.
However, such experimentation will not be undue making the objectives
of this invention inoperative with respect to any molecular sieve
structure already known in the art. In addition, the process of
this invention creates the potential for the development of novel
molecular sieves.
In the following examples, the conversion levels of the products
were measured by x-ray powder diffraction pattern ("XRD").
The crystallinity of the product was compared to the crystallinity
of a reference sample by calculating the ratio of the peak areas
(A): crystallinity=A.sub.sample /A.sub.reference. For zeolite beta,
the ratio of the peak areas at 2.theta.=22.4.degree. was used. The
reference H-beta sample was obtained from UOP. For ZSM-5 and silicalite-1
the crystallinity was calculated by the ratio between the sum of
the peaks between 2.theta.=23.degree. and 25.degree.. The reference
Na-ZSM-5 sample was obtained from UOP. For zeolite Y the crystallinity
was calculated by the ratio of the peaks areas at 23.6 26.9 and
31.3.degree.. The reference NaY sample was obtained from Akzo. All
samples were washed with an excess of water on a filter, and dried
in air at 120.degree. C. before measurement of the X-ray spectrum.
EXAMPLE 1
Conversion to Zeolite Beta
Davison.RTM. Sylopol.RTM. 948 silica gel 50 .mu.m spheres (486
grams) were fully impregnated to the incipient wetness point by
an aqueous Al(NO.sub.3).sub.3 solution (made with 202 grams of Al(NO.sub.3).sub.3.9H.sub.2
O (Merck) dissolved in 800 grams of water), over a one-hour period,
then dried in air at 120.degree. C. to a constant weight. After
drying, the dried impregnated silica spheres were calcined at 500.degree.
C. for 2 hours, resulting in a 5.35 weight % Al.sub.2 O.sub.3 content
and a Si/Al ratio of 15.
These spheres (1.10 grams) were mixed with 1.10 grams of an aqueous
35 weight % tetraethylammonium hydroxide (Aldrich) solution and
0.57 gram of an aqueous 3.68 weight % NaNO.sub.3 solution, corresponding
to a molar oxide ratio of:
The mixture was placed in a 35 ml autoclave with a 4 ml Teflon.RTM.
insert and heated at 155.degree. C. for 44 hours. The product, which
contained crystallite clusters of approximately 250 nm and large
pores between these clusters, consisted of 50 .mu.m particles with
a framework-structure, as determined by scanning electron microscopic
analysis, similar to the original Davison.RTM. Sylopol.RTM. 948
silica gel 50 .mu.m spheres. The crystallinity of the zeolite beta
product was 78%.
EXAMPLE 2
Conversion to Zeolite Beta
Shell.RTM. (S 980 A 3.0) 3.0 mm silica spheres (3.09 grams) were
fully impregnated to incipient wetness by a mixture of 1.25 grams
of Al(NO.sub.3).sub.3.9H.sub.2 O dissolved in 6.00 grams of water
to obtain a Si/Al ratio of 15 in the impregnated product. The impregnated
product was air dried at 120.degree. C. to a constant weight. Two
grams of these impregnated spheres were additionally impregnated
with an aqueous 35 weight % tetraethylarnmonium hydroxide solution
and 1.04 grams of an aqueous 3.68 weight % NaNO.sub.3 solution,
giving a molar oxide ratio of
The mixture was placed in a 30 ml stainless steel autoclave with
a 25 ml Teflon.RTM. insert. After heating for 44 hours at 155.degree.
C., the product possessed 82% zeolite beta crystals and the morphology
of the Shell 3.0 nmm silica spheres.
EXAMPLE 3
Conversion to Zeolite Beta
Davison.RTM. Sylopol.RTM. 948 silica gel 50 .mu.m spheres were
air-milled to a particle size of 3.5 .mu.m. Then 3.10 grams of the
milled particles were fully impregnated to incipient wetness by
a mixture of 1.25 grams of Al(NO.sub.3).sub.3 and 10.0 grams of
water to result in a Si/Al ratio of 15 and then dried in air at
120.degree. C. to a constant weight. Two and one-half grams of the
milled and impregnated particles were impregnated with 2.50 grams
of an 35 weight % aqueous tetraethylammonium hydroxide solution
and 1.25 grams of an 3.68 weight % aqueous NaNO.sub.3 solution,
resulting in a molar oxide ratio of
The mixture was placed in a 35 ml stainless steel autoclave with
a 10 ml Teflon.RTM. insert. After 46 hours at 155.degree. C., the
powder had been converted to 47 weight % zeolite beta. After ultrasonic
treatment for 3 hours, the individual particle size of 3-5 .mu.m
was regained. The average crystallite size, according to TEM analysis
(transmission electron microscopy), was 75-100 nm. The individual
crystallites had a more ordered stacking than the reference zeolite
beta powder.
EXAMPLE 4
Conversion to Zeolite Beta
As described in Example 1 above, 3.10 grams of Davison.RTM. Sylopol.RTM.
948 silica gel 50 .mu.m spheres were fully impregnated to incipient
wetness by a solution made from 1.26 grams of Al(NO.sub.3).sub.3.9H.sub.2
O and 8.60 grams of water, dried in air at 120.degree. C. and calcined
at 400.degree. C. for 3 hours, cooled to room temperature and calcined
at 800.degree. C. for 3 hours, resulting in 5.35 weight % Al.sub.2
O.sub.3 content (Si/Al ratio is 15).
Two and one-half grams (2.50 grams) of these spheres were impregnated
with 2.50 grams of an aqueous 35 weight % tetraethylammoniurn hydroxide
solution and 1.25 grams of an aqueous 3.68 weight % NaNO.sub.3 solution.
The molar oxide ratio was:
The mixture was placed in a 35 ml stainless steel autoclave with
a 10 ml Teflon.RTM. insert. After 44 hours at 160.degree. C., the
spheres were converted to 94 weight % zeolite beta. According to
SEM analysis, the original size and shape of the spheres were not
affected by the hydrothermal processing. Large pores were present
in the converted spheres and crystallite clusters of 0.20-0.25 .mu.m
were formed. Typical features observed by TEM are crystallite sizes
of 50-100 mm and a more ordered stacking of crystallites than in
the reference zeolite beta powder.
EXAMPLE 5
Conversion to Zeolite Beta
As described in Example 1 above, Davison.RTM. Sylopol.RTM. 948
silica gel 50 .mu.m spheres were impregnated with an aqueous Al(NO.sub.3).sub.3.9H.sub.2
O solution, dried in air at 120.degree. C. and calcined at 400.degree.
C. for 3 hours, cooled to room temperature, resulting in 5.35 weight
% Al.sub.2 O.sub.3 content (Si/Al ratio is 15).
Two and one-half grams (2.50 grams) of these spheres were impregnated
with 1.65 grams of an aqueous 35 weight % tetraethylammonium hydroxide
solution and 1.25 grams of an aqueous 3.68 weight % NaNO.sub.3 solution.
The molar oxide ratio was:
The mixture was placed in a 35 ml stainless steel autoclave with
a 10 ml Teflon.RTM. insert. After 120 hours at 160.degree. C. the
zeolite beta crystallinity of the product was 32.4%, as measured
by XRD versus the reference sample, while maintaining according
to light microscopy the sphere morphology of the Davison.RTM. Sylopol.RTM.
948 silica gel 50 .mu.m spheres.
EXAMPLE 6
Conversion to ZSM-5
As described in Example 1 above, 3.10 grams of Davison.RTM. Sylopol.RTM.
948 silica gel 50 .mu.m spheres were impregnated with a mixture
of 0.63 gram Al(NO.sub.3).sub.3.9H.sub.2 O and 11.5 grams of water
to obtain a Si/Al ratio of 30 and dried in air at 120.degree. C.
to a constant weight. Two and one-half grams (2.50 grams) of these
spheres were impregnated with 1.25 grams of an aqueous 35 weight
% tetrapropylammonium hydroxide solution and 1.25 grams of an aqueous
3.68 weight % NaNO.sub.3 solution, giving a molar oxide ratio of:
The mixture was placed in a 35 ml stainless steel autoclave with
a 10 ml Teflon.RTM. insert. After 25 hours at 158.degree. C. the
ZSM-5 crystallinity of the product was 25.1% as measured by XRD
versus the reference sample. The particle shape and size of the
parent amorphous framework-structure spheres were retained in the
product. Large pores were formed in the product spheres upon conversion
to ZSM-5. According to SEM analysis, the product spheres contained
cubic crystals sized betveen 0.5 .mu.m and 1.5 .mu.m.
EXAMPLE 7
Conversion to ZSM-5
Shell.RTM. (S 980 A 3.0) 3.0 mm silica spheres (6.20 grams) were
fully impregnated to incipient wetness by a mixture of 1.26 grams
of Al(NO.sub.3).sub.3.9H.sub.2 O dissolved in 12.08 grams of water
to obtain a Si/Al ratio of 30 in the impregnated product. The impregnated
product was air dried at 120.degree. C. to a constant weight. Two
and one-half grams (2.50 g) of these spheres were impregnated with
1.25 g of an aqueous 40 weight % tetrapropylammonium hydroxide solution
and 0.55 g of an aqueous 3.68 weight % NaNO.sub.3 solution, corresponding
to the following molar oxide ratio:
The mixture was placed in a 35 ml stainless steel autoclave with
10 ml Teflon.RTM. insert. After 18 hours at 155.degree. C. the S
980 spheres were partially converted to ZSM-5 (10% crystallinity),
while retaining the original S 980 sphere morphology.
EXAMPLE 8
Conversion to Silicalite-1
In this example, 1.10 g of Davison.RTM. Sylopol.RTM. 948 silica
gel 50 .mu.m spheres were fully impregnated to incipient wetness
by mixing with 0.55 g of an aqueous 40 weight % tetrapropylammonium
hydroxide solution and 0.55 g of an aqueous 3.68 weight % NaNO.sub.3
solution, giving the following molar oxide ratio:
The mixture was placed in a 35 ml stainless steel autoclave with
4 ml Teflon.RTM. insert. After 23 h at 165.degree. C. the impregnated
spheres were partially converted to silicalite-1 (crystallinity
11%). By light microscopy it was observed that the particle size
and shape of the precursor material was maintained.
EXAMPLE 9
Conversion to Zeolite Y
In this example, 495 grams of Davison.RTM. Sylopol.RTM. 948 silica
gel 50 .mu.m spheres were fully impregnated to incipient wetness
by a mixture of 294 grams of Al(NO.sub.3).sub.3 and 770 grams of
water, dried in air at 120.degree. C. to a constant weight, and
calcined in at 500.degree. C. for 2 hours. The resulting Al.sub.2
O.sub.3 content was 7.50 wt %. Ten grams of these spheres were impregnated
with 24.30 grams of a mixture of 13.44 grams of Al(NO.sub.3).sub.3.9H.sub.2
O and 35.3 of water to obtain a Si/Al ratio of 4.75 dried in air
at 120.degree. C. to constant weight and calcined at 300.degree.
C. for 6 hours. Finally the spheres were fully impregnated with
24.44 grams of the above mentioned Al(NO.sub.3).sub.3 solution to
obtain a Si/Al ratio of 3 dried in air at 120.degree. C. to a constant
weight and calcined at 300.degree. C. for 6 hours. Two grams of
these spheres were impregnated with 3.50 g of an aqueous 20% NaOH
solution. The resulting molar oxide ratio was:
The impregnated spheres were heated at 100.degree. C. in a 50 ml
polypropylene bottle. After 16 hours, the crystallinity of the product
was 102% zeolite Y in the form of crystallite clusters of 1.5-2.0
.mu.m in size. By TEM it was found that these crystallite clusters
consisted of ordered 50-100 nm crystals. According to SEM analysis,
the product's shape and size was that of the parent particles with
large pores within the sphere structure.
EXAMPLE 10
Conversion to Zeolite Y
Davison.RTM. Sylopol.RTM. 948 silica gel 50 .mu.m spheres (486
grams) were fully impregnated to incipient wetness with an aqueous
Al(NO.sub.3).sub.3 solution (made with 202 grams of Al(NO.sub.3).sub.3.9H.sub.2
O dissolved in 800 grams of water), then dried in air at 120.degree.
C. to a constant weight. After drying, the dried impregnated silica
spheres were calcined at 500.degree. C. for 2 hours, resulting in
a 5.35 weight % Al.sub.2 O.sub.3 content and a Si/Al ratio of 15.
The spheres were jet milled to a particle size of 3-5 .mu.m. Of
these particles 10.03 grams were fully impregnated to incipient
wetness by 25.42 grams of a mixture of 15.84 grams of Al(NO.sub.3).sub.3.9H.sub.2
O and 35.0 g of water to obtain a Si/Al ratio of 5.0 dried in air
at 120.degree. C. to a constant weight, and calcined at 300.degree.
C. for 6 hours. The particles were then impregnated with 25.42 grams
of the above-mentioned Al(NO.sub.3).sub.3 solution to obtain a Si/Al
ratio of 3 dried in air at 120.degree. C. to a constant weight,
and calcined at 300.degree. C. for 6 hours. Of these particles,
2.00 grams were fully impregnated to incipient wetness by 4.00 grams
of an aqueous 20% NaOH solution. The resulting molar oxide ratio
was:
The mixture was heated at 100.degree. C. in a 100 ml polypropylene
bottle. After 22 hours the crystallinity of the product was 86%
zeolite Y. After ultrasonic treatment for 3 hours, particle size
measurements indicated a typical particle size equal to that of
the parent material. |