Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
3~
P0 ~ SYNTHESIS
The present invention relates to layered oxides containing
interlayer polymeric oxides and to their synthesis.
Many layered materials are known which have
three-dimensional structures which exhibit their strongest chemical
bonding in only two dimensions. In such materials, the stronger
chemical bonds are formed in two-dimensional planes and a
three-dimensional solid is formed by stacking such planes on top of
each other. However, the interactions between the planes are weaker
than the chemical bonds holding an individual plane together. The
weaker bonds generally arise from interlayer attractions such as Van
der Waals forces, electrostatic interactions, and hydrogen bcnding.
~n those situations where the layered structure has electrically
neukral sheets interacting with each other solely through Va~ der
Waals forces, a high degree of lubricity is manifested as the planes
slide across each other without encountering the energy barriers
that arise with strong interlayer bonding. Graphite is an example
of such a material. The silicate layers of a number of clay
materials are held together by electrostatic attraction provided by
ions located between the layers. In addition, hydrogen bonding
interactions can occur directly between complementary sites Dn
ad~jacent layers, or can be provided by interlamellar bridging
molecules.
Layered materials such as clays may be modified to increase
their surFace area. In particular, the distance between the layers
can be increased substantially by absorption o~ various swelling
agents such as water, ethylene glycol, amines and ketones, which
enter the interlamellar space and push the layers apart. However,
the interlamellar spaces of such layered materials tend to collapse
3~
F-3812 --2--
when the molecules occupying the space are removed by, for example,
exposing the clays to high temperatures. Accordingly, such layered
materials having enhanced surface area are not suited for use in
chemical processes involving even moderately severe conditions.
The extent of interlayer separation can be estimated by
using standard techniques such as X-ray diffraction to determine the
basal spacing, also known as "repeat distance" or "d-spacing".
These values indicate the distance between, for example, the
uppermost margin of one layer and the uppermost margin of its
adjoininQ layer. If the layer thickness is known, the interlayer
spacing can be determined by subtracting the layer thicl<ness from
the basal spacing.
Various approaches have been taken to provide layered
materials of enhanced interlayer distance havin0 thermal stability.
Most techniques rely upon the introduction of an inorganic
"pillaring" agent between the layers of a layered material. For
exarnple, U.S. Patent 4,216,188 discloses a clay which is
cross-linked with metal hydroxide prepared from a hir~hly dilute
colloidal solution containing fully separated unit layers and a
cross-linking agent comprising a colloidal metal hydroxide
solution. However, this method requires a highly dilute forming
solution of the clay ( ~ 19/1) in order to effect full layer
separation prior to incorporation of the pillaring species, as well
as positively charged species of cross linking agents. U.S. Patent
4,248,7~9 relates to stable pillared interlayered clay prepared from
smectite clays reacted with cationic metal complexes of metals such
as aluminurn and zirconium. The resulting products exhibit high
interlayer separa-tion and thermal stability.
U.S. Patent 4,176,û90 discloses a clay composition
interlayered with polymeric cationic hydroxy metal complexes of
metals such as aluminum, zirconium and titanium. Interlayer
distances of up to 16A are claimed although only distances
restricted to about 9A are exemplified for calcined samples. These
distances are essentially unvariable and depend on the specific size
of the hydroxy metal complex.
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F-3~12 --3--
Silicon-containing materials are believed to be a highly
desirable species of pillaring agents owing to their high thermal
stability. U.S. Patent 4,367,163, for example, describes a clay
pillared with silica prepared by impregnating a clay substrate with
a silicon-containing reactant such as an ionic silicon complex,
e.g., silicon acetylacetonate, or a neutral species such as
SiC14. The clay may be swelled prior to or during silicon
impregnation with a suitable polar solvent such as methylene
chloride, acetone, benzaldehyde, or dimethylsulfoxide. This method,
lo however9 appears to provide only a monolayer of intercalated silica
resulting in a product of small spacing between layers, about 2-3 A
as determined by X-ray diffraction.
rn a first aspect, the present invention resides in a
layered product comprising a layered oxide of an element ranging ln
atomic number ~rom 13 to 15, 21 to 33, 39 to ~1, 57 to 8-3 and
greater than 9û, incluslve, and pillars separating the oxide layers,
the pillars containing a polymeric oxide of an element selected from
Group IVB of the Periodic Table and catalytically active sites and
said product having a d-spacing of at least lOA.
In a second aspect, the invention resides in a layered
product comprising a non-swellable layered oxide of an element
ranging in atomic number from 13 to 1~, 21 to 33, 39 to 51, 57 to 83
and greater than 90, inclusive9 and pillars containing at least one
polymeric oxide and catalytically active sites separating the oxide
layers.
In a third aspect, the inven-tion resides in a layered
silicate composition having pillars between the silicate layers, the
pillars containing a polymeric oxide selected from silicon,
titanium, zirconium and hafnium and further containing catalytically
active sites.
In a fourth aspect, the invention resides in a method for
preparing a layered product having adjacent layers separated by
polymeric oxide pillars9 which method comprises starting with a
layered oxide material of an element ranging in atomic number from
3;~
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13 to 15, 21 to 33, 39 to 51, 57 to 83 and greater than 90, said
layered oxide material having anionic sites associated therewith;
physically separating the layers of the oxide material by
introducing an organic cationic species between the layers at said
anionic sites; introducing between the separated layers of said
layered oxide at least one compound capable of conversion to a
polymeric oxide and at least one compound capable of conversion to
produce catalytically active sites; and converting said compounds to
produce polymeric oxide pillars containing catalytically active
sites separating adiacent layers of the layered oxide material.
The method of present invention is particularly usefu~ in
that it permits the preparation of catalytically active, layered
oxide materials of relatively high d-spacing, e.g., greater than
about lOA, preferably greater than about 2ûA, up to or even
c, c,
exceeding 3ûA, preferably up to 25A. These materials can be exposed
to severe conditions such as those encountered in calcining wi.thout
significant decrease in interlayer distance. furthermore, such
layered oxides can be prepared without the severe dilution necessary
to introduce the pillaring material as is often encountered in prior
art techniques of interlayering. Finally, by varying the size of
the organic cationic species separating the oxide layers, it is
possible to form pillared products with widely varying interlayer
spacing.
The method of the present invention utilizes a layered
oxide starting material which has interlayer cations associated
therewith. Such cations may include hydrogen ion, hydronium ion and
alkali metal cations. The starting material is then treated with a
"propping" agent comprising a source of an organic cation, such as
an organoammonium cation, in order to effect an exchange of or
addition to the interlayer cations resulting in the layers of the
starting material being propped apart. The source of organic cation
in those instances where the interlayer cations include nydrogen or
hydronium ions may include a neutral compound such as an organic
amine which is converted to a cationic analogue during the
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"propping" treatment. The foregoing treatment results in the
formation of a layered metal oxide of enhanced interlayer separation
depending upon the size of the organic cation introduced. In one
embodiment, a series of organic cation exchanges is carried out.
For example, an organic cation may be exchanged with an organic
cation of greater si~e, thus increasing the interlayer separation in
- a step-wise fashion~ Preferably, contact of the layered oxide withthe propping agent is conducted in aqueous medium so that water is
trapped within the interlayer spaces of the propped oxide.
After the ion exchange, the organic-"propped" species is
treated with a compound capable of conversion, preferably by
hydrolysis, to a polymeric oxide. The ~'propped" layered material
containing the polymeric oxide precursor is then treated to produce
polymeric oxide pillars separating the oxide layers. Where the
treatment involves hydrolysis, this may for example be carried out
using water already present in organic-"propped" layered oxide
material.
It is preferred that the organic cation deposited between
the layers be capable of being removed from the layered oxide
material without substantial disturbance or removal of the polymeric
oxide or oxide precursor. For example, organic cations such as
n-octylammonium may be removed by calcination or chemical oxidation,
preferably by calcination and preferably after the polymeric oxide
precursor has been converted to the polymeric oxide.
The resulting oxide-pillared product exhibits high surface
area, e.g., greater than 200, ~00, or even 600 rn2/g, and thermal
stability making it useful as a catalyst or catalytic support For
hydrocarbon conversion processes, for example cracking and
hydrocracking.
The layered oxides used in the present invention are
layered oxides of elements having an atomic number from 13 to 15, 21
to 33, 39 to 51, 57 to 83 or greater than 9û. Preferably, the
layered oxide is ~'non-swellable~ which is intended to distinguish
from conventional clays which contain octahedrally coordinated
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metal oxide sheets bonded to tetrahedrally coordinated silica sheets
and which undergo substantial swelling, sometimes by an essentially
unbounded amount, when contacted with water. As used herein in
relation to a layered oxide material, the term ~non-swellable" is
defined as meaning a layered oxide material which, when contacted
with at least 10 grams of water per gram of the layered oxide at
23C for 24 hours, exhibits an increase in d spacing no greater
than 5A as compared with the anyhydrous material. Included among
these materials are H2Ti307, Na2Ti307 and KTiNbO5 as
well as certain layered silicates, for example, the
metasilicatesmagadiite, natrosilite, kenyaite, makatite and
kanemite. Other suitable starting materials include layered clays,
such as bentonite, although these are swellable in water. Where the
starting layered material is a layered silicate, it has been found
lS to be preferable to treat the silicate wlth one or more polar
solven-ts prior to or durin~ exchange with the source of organic
cation. The polar solvent used should exhibit electric dipole
moments in the gas phase of at least 3.û Debyes (D), prefPrably at
least 3.5 Debyes, m~st preferably at least about 3.8D. Examples of
! 20 suitable solvents are water, dimethylsulfoxide (DMSO) and
dimethylformamide (DMF). A table of selected organic compounds and
their electric dipole moments can be found in CRC Handbook of
Chemistry and Physics, 61st Edition, 198û-1981 at pages E-64 to
E-660 It is believed that the treatment of the oxide s-tarting
material with one or more highly polar solvents facilitates the
introduction of the source of organic cation bet~een the layers of
the starting material.
In one preferred embodiment, the starting material is a
layered oxide of Group IV A metal such as titanium, zirconium and
hafnium, with a layered titanate, e.g., a trititanate such as
Na2Ti307, being particularly preferred. Trititanates are
commercially available materials whose structure consists of anionic
sheets of titanium octahedra with interlayer alkali metal cations.
A method for making such material may be found in U.S. Patent
~ L~3 Z
F-3812 --7--
7~496?993~ It is known that the interlayer distance of
Na2Ti307 may be increased by replacing interlayer sodium ions
with larger octylammonium ions. See, Weiss et al., Angew. Chem/72
Jahrg. 1960/Nr/2, pp 413-hl5. However, the organic-containing
trititanate is highly susceptible to heat which can remove the
organic material and cause collapse of the layered structure. The
present invention serves to introduce a stable polymeric oxide,
preferably silica, between adjoining layers resulting in a
heat-stable material which substantially retains its interlayer
distance upon calcination.
In another preferred embodiment, the oxide starting
mate~ial is a layered silicate, such as magadiite, either in natural
or synthetic form.
As previously stated, the starting layered oxide material
is treated with an organic compound capable of forming cationic
species such as organophosphonium or organoammonium ion, beFore
adding the polymeric oxlde source. Insertion of the organic cation
between the adjoining layers serves to physically separate the
layers in such a way as to make the layered oxide receptive to the
interlayer addition of an electrically neutral, hydrolyzable,
polymeric oxide precursor. In particular, alkylammonium cations
have been found useful in the present invention. Thus C~ and
larger alkylammonium, e.g., n-octylammonium, cations are readily
incorporated within the interlayer species of the layered oxides,
serving to prop open the layers in such a way as to allow
incorporation of the polymeric oxide precursor. The extent of the
interlayer spacing can be controlled by the size of the
organoammonium ion employed so that use of the n-propymonium cation
will achieve a d-spacing of about 10.5A, whereas to achieve a
d spacing of 20A an n-octylammonium cation or a cation o~ equivalent
length is required. Indeed, the si~e and shape of the organic
cation can affect whether or not it can be incorporated within the
layered oxide structure at all. For example, bulky cations such as
tetrapropylammonium are generally undesirable for use in the present
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method, ~ith ammonium cations derived from n-alkyl primary amines,
more preferably primary monoamines, being preferred. The organic
ammonium cations separating the oxide layers may be formed in situ
by reaction of the neutral amine species with interlayer hydrogen or
hydronium cations of the layer oxide starting material.
Alternatively where the interlayer cations of the layered oxide
starting material are alkali metal cations, the organic ammonium
cation may be formed by initially combining an amine and an aqueous
acid solution, such as hydrochloric acid, and then treating the
layered oxide with the resulting aqueous organoammonium ion
solution. In either case, the treatment is conducted in aqueous
media so that water is then available to hydroly~e the electrically
neutral, hydrolyzable polymeric oxide precursor subsequently
introduced into the "propped" product.
The polymeric oxide pillars formed between the layers of
the oxide starting material may include an oxide of zirconium or
titanium or more preferably of an element selected from Group IVB of
the Periodic Table (Fischer Scientific Cw~pany Cat. No. 5-702-10),
other than carbon, and most preferably include polymeric silica. In
addition the polymeric oxide pillars include an element which
provides catalytically active acid sites in the pillars, preferably
aluminum.
The polymeric oxide pillars are formed from a precursor
material which is preferably introduced between the layers of the
organic propped species as a cationic, or more preferably
electrically neutral, hydrolyzable compound of the desired Group IV~
elements. The precursor material is preferably an organometallic
compound which is a liquid under ambient conditions. Suitable
polymeric silica precursor materials include
tetrapropylorthosilicate, tetramethylorthosilicate and, most
preferably, tetraethylorthosilicate. Where the pillars are also
required to include polymeric alumina, a hydrolyzable aluminum
compound is contacted with the organic propped species before, after
or simultaneously with the silicon compound. Preferably, the
aluminum compound is aluminum isopropoxide.
,~ "
F-3812 __9__ ~l3~2
After hydrolysis to produce the polymeric oxide pillars and
calcination to remove the organic propping agent, the ~inal pillared
product may contain residual exchangeable cations. For example,
sodium titanate pillared with polymeric silica may contain 2-3% of
weight of residual sodium. Such residual cations can be ion
exchanged by methods well known with other cationic species to
provide or alter the catalytic activity of the pillared product.
Suitable replacement cations include cesium, cobalt, nickel, copper,
zinc, manganese9 platinum, lanthanum, aluminum and mixtures thereof.
The present invention is illustrated further by the
following examples.
In these examples, adsorption data were determined as
follows: A weighed sample was contacted with the desired pure
adsorbate vapor at a pressure less than the vapor-liquid equilibrium
pressure of the adsorbate at room temperature. Adsorption was
complete when a constant pressure in the adsorption chamber was
reached (overnight for water, 3 hours for hydrocarbons); e.g., 12 mm
of mercury for waker and 4û mm for n-hexane and cyclohexane.
Samples were then removed and weighed. The increase in weight was
calculated as the adsorption capacity of the samples. Nitrogen BET
surface areas were reported in m2Jg~ X-ray diffraction data was
obtained by standard techniques using K-alpha double-t of copper
radiation.
When Alpha Value is examined, it is noted that the Alpha
Value is an approximate indication of the catalytic cracking
activity of the catalyst compared to a standard catalyst and it
gives the relative rate constant (rate of normal hexane conversion
per volume of catalyst per unit time). It is based on the activity
of the highly active silica alumina cracking catalyst taken as an
Alpha of 1 (Rate Constant = 0.16 sec ). The Alpha Test is
described in U S. Pa-tent },354,û78 and in The Journal_of Catalysis,
Vol. IVc pp. 522-529 (August 1965).
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Example 1
a) A gel was produced by mixing 400 g Cabosil silica in
54.4 9 98% NaOH and 1.4 kg water. The gel was crystallized in a 2
liter polypropylene jar at 100C for 23 days to produce synthetic
magadiite, which was then filtered, washed with hot water and dried
at (25ûF) overnight. The dried product had the following
composition (wt%):
SiO2 83.3
Na20 6.9
A120~ O.ûl
100 9 of the dried product was added to 600 ml of distilled
water, titrated with 0.1 N HCl to a pH of 2, and held at pH of 2 for
24 hours. The product, after being filtered, washed with 8 liters
of distilled water, and air dried on the ~ilter, had 95 ppm Na.
The resultant product (80 9) was treated for 24 hours with
a solution of 80 9 of octylamine in 160 9 of DMSO, filtered, air
dried and then held for subsequent treatments.
b) A solution of tetraethylorthosilicate (TEOS) and
aluminum isopropoxide (AIP) was prepared as follows:
80 9 o~ aluminum isopropoxide (30-35~) in isobutanol (Al~a)
were placed in a 250 ml polypropylene bottle and heated in a steam
chest at lû0C for 16 hours. 51.0 9 TEOS (Baker, practical grade)
were added and this sol~tion was stirred for 3 days at room
2s temperature.
20 9 of the octylamine propped product of (a) above were
reacted with the TEOS/AIP solut;on for 3 days in a polypropylene
bottle which was tightly sealed. The slurry was filtered, air
dried, and calcined for 2 hours at 510C (950F) in air. The
final product had an alpha = 5 and the following composition (wt. %):
SiO2 72.90
A1203 16.8
* Trade Mark
~. .,
..1,. .
LL~32
F-3812 -~
Exame~es 2 and 3
Further 20 9 samples of the propped product of Example l(a)
were reacted respectively with 100 g samples of titanium
tetraisopropoxide (Example 2) and tetraethylorthosilicate
(Example 3). Each reaction was conducted at room temperature for 3
days in a sealed polypropylene bottle, whereafter the resultant
- slurry was filtered, air-dried and calcined for 2 hours at 538C
(lû00F) in air. The products had the following properties:
Composition (wt %)
lo Example Alpha SiO Al 0 Ti
2 - 2 3
2 3 53.7 0.015 27
3 1 94 0~0025
EX~MPLE 4
a) llû 9 of the acid form of synthetic magadiite prepared
in a manner analogous to Example 1 were treated with a solution of
150 g of octylamine in 300 9 of distilled water for 24 hours at room
temperature. The slurry was filtered to a wetcake, reslurried
(285 g of wetcake in 5.7 liters of distilled water), left for
approximately 1 hour at room temperature, and refiltered. The
product was composed of 238 g of paste~ e material (41.54% solids).
b) 294.2 9 of aluminum isopropoxide ~30-35%) in
isobutanol were placed in a polypropylene bottle in a steam chest
(lû0C) overnight~ 171.6 9 of solution was recovered after
overnight heating. 220 g of tetraethylorthosilicate were added to
the aluminum isopropoxide solution and the mixture was magnetically
stirred for 9 days at room temperature.
c) The product (b) was added to the product (a) then an
additional 400 9 of fresh tetraethylorthosilicate were added. This
mixture was reacted for 65 hours at room temperature in a sealed
polypropylene bottle with magnetic stirring. The slurry was
filtered with difficulty, air dried, dried overnight at 110C and
then calcined at 538C for 1 hour in flowing nitrogen followed by
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2 hours in flowing air. The final product had an alpha = 10 and the
following composition (wt %):
SiO2 83.1
A1203 8.7
The surface area and sorption properties of the calcined
magadiites obtained in Examples 1 - 4 are summarized in the
~ollowing table:
Sorption Capac_ty
Example Surface Area m2/g H Cy-C6 n-C6
(12 Torr) (40 Torr) (40 Torr)
1 289 14.2 8.2 ~.7
2 158 9.2 4.~ 3.3
3 307 7.2 6.0 ~.3
4 450 16.3 12.3 10.9
