Molecular sieve abstract
Hybrid mesoporous molecular sieve silica compositions which have
intergrown wormhole domains and lamellar or hexagonal domains and
prepared from mixtures of water soluble silicate precursors and
amine surfactant templates through a neutralization reaction are
described. The silica compositions are stable above 600.degree.
C.
Molecular sieve claims
We claim:
1- A hybrid mesoporous silica composition comprising a framework
structure defining the mesopores which is in one domain lamellar
or hexagonal and in another domain with wormhole pores and wherein
the domains are intergrown together.
2- A composition which is a hybrid wormhole and lamellar or hexagonal
framework molecular sieve silica prepared by a neutralizing reaction
in an aqueous solution of amine surfactant; a reactive silica species
of pH between 5.0 and 10.5; aging of the solution to precipitate
the silica and removing of the silica from the solution.
3- A composition which is a hybrid wormhole and lamellar or hexagonal
molecular sieve silica prepared by a process which comprises: (a)
acidifying an aqueous solution of an amine surfactant as a structure
director with an acid selected from the group consisting of organic,
mineral and oxy acids; (b) preparing a reactive silica species in
the aqueous solution by neutralization of a basic soluble silicate
solution by mixing with the acidified amine surfactant aqueous solution
of step (a) reaching a final pH of about 5 to 10.5; (c) aging the
reactive silica species from step (b) at a temperature greater than
-20.degree. C.; (d) recovering a solid product from the aqueous
solution by removal of the solution; and (e) removing the surfactant
from the solid by calcination at 600.degree. C. in air for not less
than 30 minutes, by solvent extraction, or by treatment with a stoichiometric
amount of aqueous acid solution and washing with water, to produce
the molecular sieve silica, wherein silica possesses framework-confined
mesopores with pore diameters ranging from 1.0 to 12.0 nm, the framework-confined
channel structure comprises a hybrid wormhole and lamellar or hexagonal
framework morphology has at least one resolved powder x-ray reflection
corresponding to a pore-pore correlation spacing of 1.5 to 15.0
nm, inorganic oxide wall thickness of greater than 0.5 nm, specific
surface areas of 400 to 1400 m.sup.2/g and framework pore volumes
of 0.1 to 3 cc/g N.sub.2.
4- The composition of claim 3 wherein the silica in step (b) is
sodium silicate "water glass" with a SiO.sub.2/Na.sub.2O=1.5
to 4.0.
5- The composition of claim 3 wherein silica in step (b) is colloidal
silica or fumed silica.
6- The composition of claim 5 wherein soluble silica solution is
prepared with addition of an alkali, or organic base to dissolve
silica at a high pH greater than 12.
7- The composition of claim 3 wherein said acid is selected from
the group consisting of: HX where X=Cl, Br, I; H.sub.xY where Y=NO.sub.3.sup.-,
SO.sub.4.sup.-2 PO.sub.4.sup.-3 CO.sub.3.sup.-2 and x equals the
charge on Y; and HZ, where Z=an organic carboxylate, phenolate,
citrate, glycolate.
8- The composition of claim 1 wherein the silica is defined in
anhydrous form by the formula: SiM.sub.wO.sub.2+x wherein 1.0.gtoreq.w.gtoreq.0
and 1.5.gtoreq.x>0 and wherein M when present is one or more
metal ions.
9- The composition of claim 8 having at least one resolved X-ray
reflection and an X-ray diffraction pattern selected from the group
consisting of FIGS. 1 4 and 5.
10- The composition of claim 8 having a N.sub.2 adsorption-desorption
isotherm selected from the group consisting of FIGS. 2 and 6.
11- The composition of claim 8 having a BET surface area between
400 and 1400 m.sup.2/g.
12- The composition of claim 8 having a textural mesopore volume
from 0.01 to 3 cc/g.
13- The composition of claim 8 having TEM micrograph selected from
the group consisting of FIGS. 3A, 7A and 8A.
14- The composition of claim 8 wherein the silica contains a hexagonal
framework structure.
15- The composition of claim 1 wherein said oxide has a composition
as follows: (R-N).sub.n(SiM.sub.wO.sub.2+x) wherein (SiM.sub.wO.sub.2+x)
is written in anhydrous form without water, wherein R-N is at least
one of a selection of neutral aliphatic amines or polyamine surfactants
wherein when R-N is present, n is between about 0.05 and 2; wherein
when M is present at least one element selected from the group comprising
B, Ge, Sb, Zr, W, P, Ba, Y, La, Ce, Sn, Ti, Cr, Nb, Fe, V, Ga, Al,
Zn, Co, Ni, Mo and Cu and w and 2+x are the molar stoichiometries
of M and "O", respectively, wherein w is 0.00 to 0.30;
x is 0.00 to 1.50.
16- The composition of claim 15 having a X-ray diffraction pattern
selected from the group consisting of FIG. 4 wherein the main diffraction
peak corresponds to a basal spacing between 2.0 and 15 nm.
17- The composition of claim 15 in which the surfactant has been
removed from the silica matrix by calcination in air at 600.degree.
C.
18- The composition of claim 17 having a N.sub.2 adsorption-desorption
isotherm, the shape of which is as in FIG. 2.
19- The composition of claim 15 having a TEM micrograph selected
from the group consisting of FIGS. 3A, 7A and 8A.
20- The composition of claim 15 in which the surfactant has been
removed from silica by solvent extraction or by extraction with
an acid.
21- The composition of claim 1 wherein said silica has a composition
as follows: (SiM.sub.wO.sub.2+1) wherein (SiM.sub.wO.sub.2+1) is
written in anhydrous form without water, wherein when M is present
at least one element selected from the group comprising B, Ge, Sb,
Zr, W, P, Ba, Y, La, Ce, Sn, Ti, Cr, Nb, Fe, V, Ga, Al, Zn, Co,
Ni, Mo and Cu and w and 2+x are the molar stoichiometries of M and
"O", respectively, wherein w is 0.00 to 0.30; x is 0.00
to 1.50.
22- The composition of claim 21 having a X-ray diffraction pattern
as in FIG. 1 or FIG. 5.
23- The composition of claim 21 in which the surfactant has been
removed from the silica by calcination in air.
24- The composition of claim 23 having a N.sub.2 adsorption-desorption
isotherm shape as in FIG. 2 or FIG. 6.
25- The composition of claim 23 having a TEM micrograph image selected
from the group consisting of FIGS. 3A, 7A and 8A.
26- The composition of claim 23 in which the surfactant has been
removed from the silica matrix by solvent extraction or extraction
with an acid.
27- The composition of claim 1 wherein said silica has a composition
expressed in anhydrous form as follows: E.sub.n/q(SiM.sub.wO.sub.2+1)
where E is one or more exchange ions, q is the weighted molar average
valence of E; n/q is moles of E per mole of Si, n is the charge
on the composition excluding E, and w and 2+x, respectively, are
the molar compositions of M and oxygen in the framework, wherein
1.0.gtoreq.w.gtoreq.0 and 1.5.gtoreq.x>0.
28- The composition of claim 27 having a X-ray diffraction pattern
selected from the group consisting of FIGS. 1 and 5.
29- The composition of claim 27 in which the surfactant has been
removed from the silica by calcinations in air.
30- The composition of claim 29 having a N.sub.2 adsorption-desorption
isotherm shape as in FIG. 6.
31- The composition of claim 29 having a TEM micrograph selected
from the group consisting of FIGS. 3A, 7A and 8A.
32- The composition of claim 27 in which the surfactant has been
removed from the silica by solvent extraction or by extraction with
acid.
33- The composition of claim 27 having a N.sub.2 adsorption-desorption
isotherm shape selected from the group consisting of FIG. 6.
34- The composition of claim 1 having a TEM micrograph of FIG.
8A showing ordered pore structures in a hexagonal unit cell within
small particle materials and having a selected area electron diffraction
pattern showing polycrystalline ordering in the silica as seen by
multiple diffraction spots as shown in FIG. 8C.
35- A composition which is a hybrid molecular sieve silica prepared
by a process that comprises: (a) preparing an aqueous solution of
a amine surfactant as an organic structure director; (b) adding
a basic soluble silicate to the amine solution; (c) neutralizing
the basic amine and silicate solution with an acid selected from
the group consisting of organic, mineral and oxy acids to a final
pH of about 5.0 to 10.5 to provide a reactive silica; (d) aging
reactive silica from step (b) at temperatures greater than -20.degree.
C.; (e) recovering a solid product from the aqueous solution; and
(f) removing the surfactant by removal of the solution to provide
the molecular sieve silica, wherein the silica possesses framework-confined
mesopores with pore diameters ranging from 1.0 to 12.0 nm, the framework-confined
channel structure comprises the hybrid of a wormhole and lamellar
or wormhole framework morphology, has one resolved powder X-ray
reflection corresponding to a pore-pore correlation spacing of 1.5
to 15.0 nm, inorganic oxide wall thickness of greater than 0.5 nm,
specific surface areas of 400 to 1400 m.sup.2/g and framework pore
volumes of 0.2 to 3.0 cc/g N.sub.2.
36- A composition which is a hybrid molecular sieve silica prepared
by a process which comprises: (a) acidifying an aqueous solution
of an amine surfactant containing an alkyl chain with 6 to 36 carbon
atoms as the organic structure director with an acid selected from
the group consisting of organic, mineral and oxy acids; (b) preparing
a reactive silica species by addition of a soluble silicate to the
acidified amine surfactant reaching a pH of less than 4; (c) titrating
the reactive silica with a base to a final pH of about 5.0 to 10.5;
(d) aging reactive silica from step (b) at temperatures greater
than -20.degree. C.; (e) recovering a solid product from the aqueous
solution; and (f) removing the surfactant from the solid product
to provide the molecular sieve silica, wherein the resulting inorganic
oxide possesses framework-confined mesopores with pore diameters
ranging from 10 to 12.0 nm, the framework-confined channel structure
comprises the hybrid of a wormhole and lamellar or hexagonal framework
morphology, has at least one resolved powder x-ray reflection corresponding
to a pore-pore correlation spacing of 1.5 to 15.0 nm, inorganic
oxide wall thickness of greater than 0.5 nm, specific surface areas
of 400 to 1400 m.sup.2/g and framework pore volumes of 0.2 to 3.0
cc/g N.sub.2.
37- A process for the preparation of a hybrid wormhole and lamellar
or hexagonal molecular sieve silica which comprises: (a) reacting
in an aqueous solution, an amine surfactant and a reactive silica
species of pH between 5.0 and 10.5; (b) aging the solution to precipitate
the silica; and (c) removing the silica from the solution.
38- A process for the preparation of a hybrid molecular sieve silica
which comprises: (a) providing a protonated amine surfactant solution
with a pH below 7.0; (b) reacting the protonated amine surfactant
solution with a mixture of a base and a soluble silicate solution
to produce a reactive silica species at a final pH between about
5.0 and 10.5; (c) aging the reactive silica species in the solution
of step (b) at a temperature greater than -20.degree. C. to form
a precipitated product which is the silica in the solution; and
(d) recovering the precipitated product from the solution.
39- The process of claim 38 wherein the surfactant is removed from
the precipitated product.
40- A process for the preparation of a hybrid molecular sieve silica
which comprises: (a) acidifying surfactant solution of a neutral
amine surfactant with an acid thereof to produce a pH below 7.0;
(b) forming a reactive silica species by neutralization of a soluble
silicate solution with the surfactant solution of step (a) to provide
a final pH of about 5.0 to 10.5; (c) aging the reactive silica species
in the solution of step (b) at a temperature greater than -20.degree.
C. to form a precipitated product which is the silica composition
in the solution; and (d) recovering the precipitated product from
the solution.
41- The process of claim 40 wherein soluble silica solution is
a sodium silicate with SiO.sub.2/OH.sup.- ratio of between 0.7 and
2.
42- The process of claim 40 wherein the acid is an organic acid.
43- The process of claim 42 wherein the acid is selected from the
group consisting of acetic, glycolic, formic and citric acid.
44- The process of claim 40 wherein the surfactant is removed by
calcination, solvent extraction or acid washing.
45- The process of claim 40 with the additional step (d) of removing
the surfactant and by calcination of the precipitated product in
air for not less than 30 minutes.
46- A process for the preparation of a hybrid molecular sieve silica
which comprises: (a) providing an aqueous solution of a water soluble
silicate at a pH greater than 9; (b) combining the aqueous solution
with a neutral amine surfactant and an acid to produce a resulting
mixture wherein the pH of the mixture is between about 5.0 and 10.5;
(c) aging the resulting mixture at a temperature between -20.degree.
and 100.degree. C. until the hybrid molecular sieve silica is formed;
and (d) removing at least the aqueous solution to produce the hybrid
molecular sieve silica.
47- A process for the preparation of a hybrid molecular sieve aluminosilicate
which comprises: (a) providing an aqueous solution of a water soluble
aluminate and silicate in a molar ratio of aluminate to silicate
of between about 0.01 and 1.0 at a pH greater than 9; (b) combining
the aqueous solution with a neutral amine surfactant and an acid
in aqueous solution to produce a resulting mixture wherein the pH
of the mixture to be between about 5.0 and 10.5; (c) aging the resulting
mixture at a temperature between -20.degree. and 100.degree. C.
until the hybrid molecular sieve aluminosilicate is formed; and
(d) removing at least the aqueous solution to produce the hybrid
molecular sieve aluminosilicate.
48- A process for the preparation of a hybrid molecular sieve aluminosilicate
which comprises: (a) providing an aqueous solution of a water soluble
silicate at a pH greater than 9; (b) combining the aqueous solution
with a neutral amine surfactant, an aluminum salt and an acid in
aqueous solution to produce a resulting mixture wherein the aluminum
to silicon molar ratio is between 0.01 and 1.0 and the pH of the
mixture to be between about 5.0 and 10.5; (c) aging the resulting
mixture at a temperature between -20.degree. and 100.degree. C.
until the hybrid molecular sieve aluminosilicate is formed; and
(d) removing at least the aqueous solution to produce the hybrid
molecular sieve aluminosilicate.
49- The process of claim 48 wherein in step (d) the surfactant
and water are removed from the aluminosilicate so that aluminosilicate
is dry.
50- The process of claim 48 wherein the aluminosilicate is calcined.
51- The process of claim 48 wherein the aluminum salt is selected
from the group consisting of aluminum nitrate, aluminum chloride,
aluminum sulfate and a cationic aluminum oligomer.
52- The composition of claim 1 derived from a mixture of a neutral
amine, basic silicate and acid in an aqueous solution to produce
a pH between about 5 to 10.5.
53- The composition of claim 1 derived from a mixture of a protonated
amine and a basic silicate in an aqueous solution to produce a pH
between about 5.0 and 10.5.
Molecular sieve description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application relies for priority on application
Ser. No. 60/197033 filed Apr. 13 2000.
BACKGROUND OF THE INVENTION
[0003] (1) Field of the Invention
[0004] The present invention relates to thermally stable hybrid
molecular sieve silicas generally having uniform pores, and specifically
to calcined silicas. The silicas have hybrid wormhole and either
lamellar or hexagonal structures intergrown together. In particular,
the present invention relates to the use of water soluble silicates
and preferably neutral amine surfactants surfactants for the preparation
of these thermally stable silicas. In particular the present invention
relates to mesoporous silicas having a pore size between about 1.0
and 12 nm.
[0005] (2) Description of Related Art
[0006] The disclosure by Mobil in 1992 (Beck, J. S., et al., J.
Am. Chem. Soc. 114 10834 (1992)) of the synthesis of mesoporous
aluminosilicate molecular sieves (M41S materials) utilizing assemblies
of cationic organic molecules (micelles) as structure directors
led to a vast amount of research into this field. To date, the synthesis
of mesoporous molecular sieves can be classified into several general
pathways according to their organic-inorganic interfacial interactions.
Electrostatic charge matching (Beck, J. S., et al., J. Am. Chem.
Soc. 114 10834 (1992); Huo, Q., et al., Chem. Mater. 6 1176 (1994);
Huo, Q., et al., Nature 368 317 (1994)), H-bonding (Tanev, P. T.,
et al., Science 267 865 (1994); and Bagshaw, S. A., et al., Angwen.
Chem. Int. Ed. Engl. 36 516 (1997)), and dative bonding interactions
(Antonelli, D. M., et al., Angwen. Chem. Int. Ed. Engl., 35 426
(1996); and Antonelli, D. M., et al., Chem. Mater 8 874 (1996))
at the organic micelle-inorganic interface have all been successfully
utilized in the formation of mesostructured inorganic materials.
[0007] Electrostatic charge matching pathways utilize coulombic
interactions between the charged structure directing surfactant
assemblies (micelles) and ionic silica species in the assembly of
stable inorganic framework structures. As reported by Mobil, synthesis
of the M41S family of molecular sieves relies on cooperative assembly
between cationic quaternary ammonium surfactant micelles (S.sup.+)
and anionic water-soluble silicates (I.sup.-). Synthesis under hydrothermal
conditions results in mesoporous silicates that possess a high degree
of framework pore order. M41S materials are generally large particle
materials that have uniform pore diameters, significantly large
surface areas (.about.800-1200 m.sup.2/g) and little to no observable
textural mesoporosity (Tanev, P. T., et al., Chem. Mater. 8 2068
(1996)). Due to the strong coulombic interactions between the surfactant
and the silica wall, however, a simple solvent extraction and recycling
of this costly quaternary ammonium surfactant is not possible. Surfactant
removal is accomplished either by calcinations or by an ion exchange-solvent
extraction method (Whitehurst, D. D. U.S. Pat. No. 6143879 (1992)).
[0008] The syntheses of HMS materials rely on H-bonding interactions
between the neutral amine surfactant (S.degree.) assemblies and
molecular silica precursors (I.degree.) such as tetraethylorthosilica
(TEOS) (Tanev, P. T., et al., Science 267 865 (1995)). This H-bonding
interaction is significantly weaker than the coulombic interactions
of the electrostatic pathways resulting in the disordered wormhole
pore structure typical of HMS silicas (Tanev, P. T., et al., Science
267 865 (1995); Tanev, P. T., et al., Chem. Mater. 8 2068 (1996);
and Behrens, P., Angew. Chem. Int. Ed. Engl. 35(5) 515 (1996)).
This wormhole pore structure has significant pore branching and
3-dimensional pore character. Characteristic properties of HMS silicas,
however, are similar to those of electrostatically assembled mesostructures
in their pore size distributions, surface areas, and pore volumes.
Additionally, synthesis of these silicas in highly polar solvents,
where the surfactant exists in an emulsion phase, results in small
particle materials that possess significant textural, or inter-particle,
porosity (Pauly, T. R., et al., J. Am. Chem. Soc. 121 8835 (1999)).
This fact along with the highly branched pore structure yields a
mesoporous material that exhibits unique catalytic activity due
to the enhanced access to reactive sites (Pauly, T. R., et al.,
J. Am. Chem. Soc. 121 8835 (1999)).
[0009] Long alkyl chain amine surfactants used in HMS synthesis
are significantly less costly than quaternary ammonium salts used
in the synthesis of M41S and SBA materials. The use of TEOS or other
molecular silica species, however, is considerably more expensive
than available water soluble silicate species. Thus far, however,
mesostructure synthesis using H-bonding mechanisms with neutral
amine surfactants required the use of molecular silica species.
[0010] Mesoporous molecular sieve silicas with wormhole framework
structures (e.g., MSU-X (Bagshaw, S. A., et al., Science 269 1242
(1994); Bagshaw, S. A., et al., Angwen. Chem. Int. Ed. Engl. 35
1102 (1996); Prouzet, E. et al., Angwen. Chem. Int. Ed. Engl. 36
516 (1997), and HMS (Tanev, P. t., et al., Science 267 865 (1995))
are generally more active heterogeneous catalysts in comparison
to their ordered hexagonal analogs (e.g., MCM-41 (Beck, J. S., et
al., J. Am. Chem. Soc. 114 10834 (1992); and Huo, Q., et al., Nature
368 317 (1994)), and SBA-15 (Stucky, JACS). The enhanced reactivity
has been attributed, in part, to a pore network that is connected
in three dimensions, allowing the guest molecules to more readily
access reactive centers that have been designed into the framework
surfaces (Tanev, P. T., et al., Chem. Mater. 8 2068 (1996); Whitehurst,
D. D. U.S. Pat. No. 6143879 (1992); Behrens, P. Angwen. Chem.
Int. Ed. Engl. 35(5), 515 (1996); and Pauly, T. R., et al., J. Am.
Chem. Soc. 121 8835 (1999)). All of the wormhole framework structures
reported to date have been prepared through supramolecular S.degree.I.degree.
(Tanev, P. T., et al., Science 267 865 (1995) and N.degree.I.degree.
(Bagshaw, S. A., et al., Angwen. Chem. Int. Ed. Engl. 35 1102 (1996);
Prouzet, E., et al., Angwen. Chem. Int. Ed. Engl. 36 516 (1997))
assembly pathways wherein I.degree. is an electrically neutral silica
precursor (typically, tetraethylorthosilicate, TEOS), SO is a neutral
amine surfactant, and N.degree. is a neutral di- or tri-block surfactant
containing polar polyethylene oxide (PEO) segments. One disadvantage
of these pathways, as with other assembly pathways based on TEOS,
is the high cost of the hydrolyzable silicon alkoxide precursor.
Greater use of wormhole framework structures as heterogeneous catalysts
can be anticipated if a more efficient approach to either S.degree.I.degree.
or N.degree.I.degree. assembly is devised based on the use of low
cost soluble silicate precursors, without sacrificing the intrinsically
desirable processing advantages of these pathways (e.g., facile
removal and recycling of the surfactant).
[0011] Recently, Guth and co-workers reported the preparation of
disordered silica mesostructures by precipitation from sodium silicate
solutions over a broad range of pH in the presence of TRITON-X 100
an N.degree. surfactant (Sierra, L., et al., Adv. Mater 11(4) 307
(1999); and Sierra, L., et al., Microporous and Mesoporous Materials
27 243 (1999)). The retention of a mesostructure was observed up
to a calcination temperature of 480.degree. C., but the complete
removal of the surfactant at 600.degree. C. led either to the extensive
restructuring of the silica framework, as indicated by the loss
of mesoporosity or the formation of a completely amorphous material.
In contrast wormhole MSU-X and HMS mesostructures are structurally
stable to calcination temperatures in excess of 800.degree. C.
[0012] Of interest is the use of an aqueous acid solution to extract
an amine surfactant template from the as-formed mesoporous silica
composition. This is reported by Cassiers et al., Royal Society
of Chemistry 2489-2490 (2000).
[0013] U.S. Pat. Nos. 5800799 6027706 5622684 5795559
5855864 5672556 5840264 5800800 5785946 and 5712402
are generally related to the present invention.
OBJECTS
[0014] There is a need for mesoporous silica compositions with
improved properties. There is also a need for mesostructured silica
compositions which are economical to prepare. These and other objects
will become increasingly apparent by reference to the following
description and the drawings.
SUMMARY OF THE INVENTION
[0015] The present invention relates to hybrid mesoporous silica
compositions in which the framework pore structure is defined by
the intergrowth of nano-domains of both wormhole framework pore
structures and either lamellar or hexagonal framework pore structures.
Typically, the nano-domains are of 100 nm or less in diameter and
do not possess a distinct boundary between adjacent domains.
[0016] The present invention relates to a hybrid molecular sieve
silica composition comprising a framework structure defining the
mesopores which is in one domain lamellar or hexagonal and in another
domain with wormhole pores and wherein the domains are intergrown
together. Typically the domain sizes are 100 nm or less.
[0017] The present invention also relates to a composition which
is a hybrid wormhole and lamellar or hexagonal framework molecular
sieve silica prepared by a neutralizing reaction in an aqueous solution
of amine surfactant; a reactive silica species of pH balance 5 and
10.5; aging of the solution to precipitate the silica and removing
of the silica from the solution.
[0018] The present invention particularly relates to a composition
which is a hybrid wormhole and lamellar or hexagonal molecular sieve
silica prepared by a process which comprises:
[0019] (a) acidifying an aqueous solution of an amine surfactant,
preferably containing 6 to 36 carbon atoms, as a structure director
with an acid selected from the group consisting of organic, mineral
and oxy acids;
[0020] (b) preparing a reactive silica species in the aqueous solution
by neutralization of a basic soluble silicate solution by mixing
with the acidified amine surfactant aqueous solution of step (a)
reaching a final pH of about 5 to 10.5;
[0021] (c) aging the reactive silica species from step (b), preferably
for no less than 5 minutes, at a temperature greater than -20.degree.
C.;
[0022] (d) recovering a solid product from the aqueous solution
by removal of the solution; and
[0023] (e) removing the surfactant from the solid by calcination
at 600.degree. C. in air for not less than 30 minutes, by solvent
extraction, or by treatment with a stoichiometric amount of aqueous
acid solution and washing with water, to produce the molecular sieve
silica, wherein silica possesses framework-confined mesopores with
pore diameters ranging from 1.0 to 12.0 nm, the framework-confined
channel structure comprises a hybrid wormhole and lamellar or hexagonal
framework morphology has at least one resolved powder x-ray reflection
corresponding to a pore-pore correlation spacing of 1.5 to 15.0
nm, inorganic oxide wall thickness of greater than 0.5 nm, specific
surface areas of 400 to 1400 m.sup.2/g and framework pore volumes
of 0.2 to 2.0 cc/g N.sub.2 preferably with textural pore volumes
of 0.01 to 3 cc/g N.sub.2.
[0024] The present invention further relates to a composition which
is a hybrid molecular sieve silica prepared by a process that comprises:
[0025] (a) preparing an aqueous solution of a amine surfactant
as an organic structure director;
[0026] (b) adding a basic soluble silicate to the amine solution;
[0027] (c) neutralizing the basic amine and silicate solution with
an acid selected from the group consisting of organic, mineral and
oxy acids to a final pH of about 5.0 to 10.5 to provide a reactive
silica;
[0028] (d) aging reactive silica from step (b) at temperatures
greater than -20.degree. C.;
[0029] (e) recovering a solid product from the aqueous solution;
and
[0030] (f) removing the surfactant by removal of the solution to
provide the molecular sieve silica, wherein the silica possesses
framework-confined mesopores with pore diameters ranging from 1.0
to 12.0 nm, the framework-confined channel structure comprises the
hybrid, a wormhole and lamellar or wormhole framework morphology,
has one resolved powder X-ray reflection corresponding to a pore-pore
correlation spacing of 1.5 to 15.0 nm, inorganic oxide wall thickness
of greater than 0.5 nm, specific surface areas of 400 to 1400 m.sup.2/g
and framework pore volumes of 0.2 to 3.0 cc/g N.sub.2 and preferably
textural pore volumes of 0.01 to 3 cc/g N.sub.2.
[0031] The present invention further relates to a composition which
is a hybrid molecular sieve silica prepared by a process which comprises:
[0032] (a) acidifying an aqueous solution of an amine surfactant
containing an alkyl chain with 6 to 36 carbon atoms as the organic
structure director with an acid selected from the group consisting
of organic, mineral and oxy acids;
[0033] (b) preparing a reactive silica species by addition of a
soluble silicate to the acidified amine surfactant reaching a pH
of less than 4;
[0034] (c) titrating the reactive silica with a base to a final
pH of about 5.0 to 10.5;
[0035] (d) aging reactive silica from step (b) at temperatures
greater than -20.degree. C.;
[0036] (e) recovering a solid product from the aqueous solution;
and
[0037] (f) removing the surfactant from the solid product to provide
the molecular sieve silica, wherein the resulting inorganic oxide
possesses framework-confined mesopores with pore diameters ranging
from 10 to 12.0 nm, the framework-confined channel structure comprises
the hybrid of a wormhole and lamellar or hexagonal framework morphology,
has at least one resolved powder x-ray reflection corresponding
to a pore-pore correlation spacing of 1.5 to 15.0 nm, inorganic
oxide wall thickness of greater than 0.5 nm, specific surface areas
of 400 to 1400 m.sup.2/g and framework pore volumes of 0.2 to 2.0
cc/g N.sub.2 and textural pore volumes of 0.01 to 3 cc/g N.sub.2.
[0038] The present invention relates to a process for the preparation
of a hybrid wormhole and lamellar or hexagonal molecular sieve silica
which comprises:
[0039] (a) reacting in an aqueous solution, an amine surfactant
and a reactive silica species of pH between 5 and 10.5;
[0040] (b) aging the solution to precipitate the silica; and
[0041] (c) removing the silica from the solution.
[0042] The present invention further relates to a process for the
preparation of a hybrid molecular sieve silica which comprises:
[0043] (a) providing a protonated amine surfactant solution with
a pH below 7.0;
[0044] (b) reacting the protonated amine surfactant solution with
a mixture of a base and a soluble silicate solution to produce a
reactive silica species at a final pH between about 5 and 10.5;
[0045] (c) aging the reactive silica species in the solution of
step (b) at a temperature greater than -20.degree. C. to form a
precipitated product which is the silica in the solution; and
[0046] (d) recovering the precipitated product from the solution.
[0047] The present invention further relates to a process for the
preparation of a hybrid molecular sieve silica which comprises:
[0048] (a) acidifying a surfactant solution of a neutral amine
surfactant with an acid thereof to produce a pH below 7.0;
[0049] (b) forming a reactive silica species by neutralization
of a soluble silicate solution with the surfactant solution of step
(a) to provide a final pH of about 5.0 to 10.5;
[0050] (c) aging the reactive silica species in the solution of
step (b) at a temperature greater than -20.degree. C. to form a
precipitated product which is the silica in the solution; and
[0051] (d) recovering the precipitated product from the solution.
[0052] The present invention further relates to a process for the
preparation of a hybrid molecular sieve silica which comprises:
[0053] (a) providing an aqueous solution of a water soluble silicate
at a pH greater than 9;
[0054] (b) combining the aqueous solution with a neutral amine
surfactant and an acid to produce a resulting mixture wherein the
pH of the mixture is between about 5.0 and 10.5;
[0055] (c) aging the resulting mixture at a temperature between
-20.degree. and 100.degree. C. until the hybrid molecular sieve
silica is formed; and
[0056] (d) removing at least the aqueous solution to produce the
hybrid molecular sieve silica.
[0057] The present invention further relates to a process for the
preparation of a hybrid molecular sieve aluminosilicate which comprises:
[0058] (a) providing an aqueous solution of a water soluble aluminate
and silicate in a molar ratio of aluminate to silicate of between
about 0.01 and 1.0 at a pH greater than 9;
[0059] (b) combining the aqueous solution with neutral amine surfactant
and an acid in aqueous solution to produce a resulting mixture wherein
the pH of the mixture to be between about 5.0 and 10.5;
[0060] (c) aging the resulting mixture at a temperature between
-20.degree. and 100.degree. C. until the hybrid molecular sieve
aluminosilicate is formed; and
[0061] (d) removing at least the aqueous solution to produce the
hybrid molecular sieve aluminosilicate.
[0062] Further the present invention relates to a process for the
preparation of a hybrid molecular sieve alumino-silicate which comprises:
[0063] (a) providing an aqueous solution of a water soluble silicate
at a pH greater than 9;
[0064] (b) combining the aqueous solution with a neutral amine
surfactant, an aluminum salt and an acid in aqueous solution to
produce a resulting mixture wherein the aluminum to silicon molar
ratio is between 0.01 and 1.0 and the pH of the mixture to be between
about 5.0 and 10.5;
[0065] (c) aging the resulting mixture at a temperature between
-20.degree. and 100.degree. C. until the hybrid molecular sieve
aluminosilicate is formed; and
[0066] (d) removing at least the aqueous solution to produce the
hybrid molecular sieve aluminosilicate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0067] FIG. 1 is an X-ray powder diffraction pattern of the calcined
product of Example 1.
[0068] FIG. 2 is a graph showing a N.sub.2 adsorption-desorption
isotherm of the calcined product of Example 1.
[0069] FIGS. 3A and 3B are TEM micrographs of the calcined product
of Example 1.
[0070] FIG. 4 is an X-ray powder diffraction pattern of the as-synthesized
product of Example 2.
[0071] FIG. 5 is an X-ray powder diffraction pattern of the calcined
product of Example 3.
[0072] FIG. 6 is a graph showing a N.sub.2 adsorption-desorption
isotherm of the calcined product of Example 3.
[0073] FIGS. 7A and 7B are TEM micrographs of the calcined product
of Example 3.
[0074] FIGS. 8A and 8B are TEM micrographs and selected area electron
diffraction pattern (SAED) pattern of the calcined product of Example
15.
[0075] FIG. 8C is a selected area electron diffraction pattern
(SAED).
DESCRIPTION OF PREFERRED EMBODIMENTS
[0076] A particular objective of this invention is to provide for
new classes of mesoporous silica compositions with hybrid framework
structures. In one embodiment of the invention, the mesoporous framework
combines the structural characteristics of a wormhole framework
with those of a lamellar framework. In another embodiment, the framework
structure integrates a wormhole framework with the structural characteristics
of a hexagonal framework. These hybrid structures cannot be described
as simple physical mixtures of wormhole and lamellar or wormhole
and hexagonal structures. Instead, the hybrid compositions of this
invention are intergrowths of mesoscopic domains that are structurally
best described as wormhole frameworks intergrown with either lamellar
or hexagonal frameworks through intergrowth of domains. Thus, a
physical separation of the intergrown domains is not possible. Another
objective of this invention is to provide a cost-efficient process
for forming the said hybrid structures using soluble silicates as
the silica precursors and amine surfactants as the structure-directing
agents. One particularly preferred silica precursor is the silica-sodium
hydroxide solution generally known as "water glass". Other
silica sources such as fumed silica can also be used in place of
soluble silicate salts, but the soluble silicates are preferred
in view of their low cost. The synthesis of the hybrid structure
are carried out under conditions of pH (between 5.0 and 10.5) where
the amine surfactant exists in solution primarily in the electronically
neutral form. To achieve the desired pH conditions, it is necessary
to add an amount of acid to the basic soluble silicate precursor
solution in order to neutralize most, if not all, of the hydroxide
ions that are initially present in the starting soluble silicate
solution. The acid used to neutralize hydroxide ions in the silicate
precursor solution can be either an organic acid, a mineral acid
or an oxyacid. The control of pH in the range 5.0 to 10.5 more
preferably in the range 6.5 to 8.5 allows the amine surfactant
and silica precursor to exist primarily in electrically neutral
form to allow for H-bonding interactions at the surfactant-silica
interface.
[0077] In particular the process uses:
[0078] (a) increased temperatures to increase pore size and (b)
increased temperatures to increase framework cross-linking and dehydroxylation
of the pore surface. Control of particle size and morphology also
is achieved by adjustment of these synthesis conditions. The compositions
of the present invention contain:
[0079] Variable alkali (metal) ions or quaternary ammonium ions
in the final product. These ions originate from the counter-cations
of the soluble silicate precursors.
[0080] Variable amine surfactant to SiO.sub.2 ratios (0.10 to 1.0).
Uniform framework pore sizes and correlated pore spacings leading
to unique disordered wormhole hybrid structures intergrown with
lamellar or hexagonal framework structures over domains of mesoscopic
size.
[0081] Framework pore diameters from 1.0 to 12.0 nm formed from
amine templated solutions. Short-range lamellar and hexagonal pore
order intergrown with wormhole frameworks obtained through judicious
choices of amine surfactant, synthesis pH, reaction stoichiometry
and reaction temperature.
[0082] Divalent and Trivalent hetero-atom substitution (Ba, Cr,
Ni, Zn, Co, Cu, Al, B, Ga, Fe, etc.) in a mesostructured silica
framework.
[0083] Tetravalent hetero-atom substitution (Ge, Ti, V, Sb, Zr,
Sn, etc.) in a mesostructured silica framework.
[0084] Penta- or Hexavalent hetero-atom substitution (P, V, W,
Mo, etc.) in a mesostructured silica framework. The compositions
of the present invention are generally referred to as "hybrid
molecular sieve silicas", or simply "silicas" or
occasionally "silicates". In using such terms the meaning
is mesostructured oxide compositions in which at least 50% of the
oxide on a mole basis is silica (SiO.sub.2) when written in anhydrous
form. The remaining portion of the framework composition may be
other metal oxides or even organosilyl groups that are integrated
into the framework structure through covalent bond formation. Exchange
cations that balance the framework charge and guest molecules, such
as water, that occupy the framework pores are not considered to
be part of the framework composition within the scope of this definition.
The framework may be negatively charged, particularly when the framework
contains aluminum and other metal ions co-condensed with SiO.sub.4
units in the framework. In this case protons, alkali metal, transition
metal or organic cations can be introduced in the framework pores
or be electrostatically linked to the framework walls to balance
the framework charge.
[0085] Further, the compositions of the present invention exhibit
at least one x-ray reflection corresponding to a d-spacing .gtoreq.3.0
nm. Still further, TEM (transmission electron microscopy) images
reveal a framework structure that integrates the structural characteristics
of a wormhole framework with the structural characteristics of either
a lamellar framework or a hexagonal framework through intergrowth
of mesoscopic domains of said structures.
[0086] The term "surfactant" means a surface active molecule
with one polar water soluble end and a non-polar oil soluble end,
thus enabling the molecule to reduce the surface tension of water.
[0087] The term "neutral amine surfactant" means a composition
which is a surface active agent initially absent of any formal charge
which acts as a template or structure director. The template is
provided with a proton from an acid during acidification to form
an onium ion in a first aqueous solution which is neutralized in
the process by the basic silica species in a second aqueous solution.
Particularly included are the neutral amine surfactants. The template
is in one preferred embodiment a neutral primary, secondary, tertiary
or polyamine or mixtures thereof, preferably having at least one
alkyl chain of from 6 to 36 carbon atoms or mixtures thereof. The
amines can also be aliphatic or aromatic amines. The amine or polyamine
surfactant may be initially protonated but upon reaction with basic
solutions of the preferred soluble silicate precursors the protons
are neutralized by reaction with the basic component of the silicate
source, thus generating a predominately neutral amine or polyamine
as the structure-directing surfactant.
[0088] The neutral amine surfactant preferably has the structural
formula: 1
[0089] R.sub.1 is a hydrophobic group preferably containing 6 to
36 carbon atoms;
[0090] R.sub.2 R.sub.4 R.sub.5 are alkyl or aryl groups or hydrogen;
[0091] R.sub.3 is an organic linker group containing one to six
carbon atoms; and
[0092] x is 0 to 6.
[0093] Synthesis of polyamine surfactants comprises reacting tallow
(animal) fatty acids with ammonia (NH.sub.3) at high temperatures
followed by the subsequent reduction of the resultant nitrile with
H.sub.2 over a ReNi catalyst at high pressures. Continued reaction
of the reduced amine with acrylonitrile (CH.sub.2CHCN), followed
by subsequent reduction with H.sub.2 results in polyamine whose
amine content and number of amine repeat units is dependent on the
number of continued alkylations of the amine with acrylonitrile.
[0094] Those skilled in the art will recognize that any amine or
protonated onium surfactants capable of bonding to inorganic precursors
through complexation or through hydrogen bonds to Si--OH or Si--O
linkages can be suitable surfactants. Polyamine based surfactants
have the advantage of low cost.
[0095] The term "soluble silicate solution" means a basic
solution of an alkali metal or organic quaternary ammonium ion silicate.
The soluble silica solution is prepared with addition of an alkali,
or organic base to dissolve silica at a high pH greater than 12.
Preferably the solution has a SiO.sub.2/M.sub.2O ratio of between
about 1.5 and 4.0 where M is an alkali metal ion or an organic
quaternary ammonium ion.
[0096] The aluminum salts are aluminum nitrate, aluminum chloride,
aluminum sulfate and a cationic aluminum oligomer.
[0097] The reaction mixture can include an organo silane selected
from the group consisting of X.sub.3SiR.sub.1 X.sub.2SiR.sub.2
or XSiR.sub.3 and mixtures thereof. X is a hydrolyzable moiety (e.g.
alkoxide or halide), which reacts with the hydroxylated silica.
[0098] The acid used in the neutralization of the reaction mixture
can be either an inorganic or organic acid. Generally this includes
organic acids, mineral acids and oxyacids. Inorganic acids are HNO.sub.3
HCl, H.sub.2SO.sub.4 and the like. Specific organic acids are acetic,
glycolic, formic and citric acids, although other acids with similar
properties are suitable.
[0099] The acid is selected from the group consisting of:
[0100] HX where X=Cl, Br, I;
[0101] H.sub.xY where Y=NO.sub.3.sup.-, SO.sub.4.sup.-2 PO.sub.4.sup.-3
CO.sub.3.sup.-2 and x equals the charge on Y; and
[0102] HZ, where Z=an organic carboxylate, phenolate, citrate,
glycolate.
[0103] The hydroxylated silica composition of the present invention
preferably has the formula:
(R-N).sub.n(SiM.sub.wO.sub.2+x)
[0104] wherein [SiM.sub.wO.sub.2+x] is written in anhydrous form
without water, wherein R-N is at least one of a selection of neutral
aliphatic amines or polyamine surfactants wherein when R-N is present,
n is between about 0.05 and 2; wherein when M is present at least
one element selected from the group comprising P, Ba, Y, La, Ce,
Sn, Ti, Cr, Nb, Fe, V, Ga, Al, Zn, Co, Ni, Mo and Cu and w and 2+x
are the molar stoichiometries of M and "O", respectively,
wherein w is 0.00 to 0.30; x is 0.00 to 1.50.
[0105] After removal of the structure-directing RN amine surfactant
by calcination, solvent extraction, or treatment with a stoichiometric
amount of acid, the compositions of the present invention also are
described in anhydrous form as SiM.sub.wO.sub.2+x wherein w and
x are as above. They may be used as adsorbents, molecular sieves,
catalysts and catalyst supports. When the calcined framework appropriately
contains M, one or more functional metallic, non-metallic or metalloid
elements, or subsequently impregnated as taught in Ger. Pat. (DD)
No. 286522 with the correct amount of a catalytically active element,
selected from the group comprising Sn, Al, Ga, Al, Rh, Nb, Re, Ag,
Cu, Cr, Pt, Pd, Ti, V, Zr, Zn, Co, Mo, Ni, Cu or mixtures thereof,
or when intercalated with transition metal inorganic metallocycles,
it can be used as a catalyst component for cracking, hydrocracking,
hydrogenation-dehydrogenation, isomerization, alkylation or oxidations
involving large and small organic substrates. Preferably the molar
ratio of deposited metal to silica is between 0.005 and 0.20 to
1. The compositions of this invention are also useful as adsorbents
for molecular separations and chromatography.
[0106] The composition with exchange counter ions is defined in
anhydrous form by the formula:
E.sub.n/q(SiM.sub.wO.sub.2+x)
[0107] where E is one or more exchange ions, q is the weighted
molar average valence of E; n/q is moles of E per mole of Si, n
is the charge on the composition excluding E, and w and x, respectively,
are the molar compositions of M and oxygen in the framework.
[0108] The synthetic process toward the new compositions of this
invention involve the preparation of solutions or emulsions of a
structure-directing surfactant and co-surfactant compound and reaction
of this solution with the inorganic silica precursor under stirring,
sonication, shaking, or quiescent conditions until formation of
the desired product is achieved and recovered as the mesoporous
silica product.
[0109] The assembled mesostructured silicas of the present invention
can be combined with other components, for example, zeolites, clays,
inorganic oxides, carbon, graphite, or organic polymers or mixtures
thereof. In this way adsorbents, ion-exchangers, catalysts, catalyst
supports or composite materials with a wide variety of properties
can be prepared. Additionally, one skilled in the art can impregnate
or encapsulate transition metal macrocylic molecules such a porphyrins
or phthalocyanines containing a wide variety of catalytically active
metal centers.
[0110] Additionally, the surfaces of the compositions can be chemically
functionalized in order to produce catalytic, hydrophilic or hydrophobic
surfaces. The surfaces may be functionalized by directly incorporating
the functionalizing agent into the mesostructure assembly process
or after synthesis of the mesostructure by reaction with various
metal salts, organometallic reagents, silylation reagents, or alkylating
reagents.
[0111] Wide-angle powder x-ray diffraction (XRD) patterns are obtained
using a Rigaku Rotaflex Diffractometer with Cu K.alpha. radiation
(.lambda.=0.154 nm). Counts were accumulated every 0.02 degrees
(20) at a scan speed of 1 degree (2.theta.)/min. X-ray scattering
provides structural data on the spatial arrangement of mesoporous
channels within the porous oxide on one length scale, and the atomic
ordering of the oxide itself on a smaller length scale. Periodically
ordered channels within an oxide and/or the crystalline oxide itself,
will provide Bragg scattering indicative of the corresponding symmetry.
Coherent X-ray scattering from disordered channel structures, however,
results in correlation peaks whose scattering intensity versus angle
is dependent on the average pore to pore distance and the uniformity
of the pore separation distance within the oxide. Differences in
the positions of the correlation peak for disordered pore systems
indicate changes in the average pore-pore separation.
[0112] N.sub.2 adsorption-desorption isotherms are obtained at
-196.degree. C. on a Micromeritics ASAP 2010 Sorptometer (Norcross,
Ga.) using static adsorption procedures in order to characterize
the pore structure. Samples were out gassed at 150.degree. C. and
10.sup.-6 Torr for a minimum of 12 hours prior to analysis. BET
surface areas were calculated from the linear part of the BET plot
according to IUPAC (Sing, K. S. W., et al., Pure Appl. Chem. 57
603 (1985)) recommendations. Pore size distribution was estimated
from the adsorption branch of the isotherm by the method of Horvath
and Kawazoe (Horvath, G., et al., J. Chem. Eng. Jpn. 16 470 (1983)).
The framework pore volume (V.sub.f) for each mesostructured sample
is taken as the volume adsorbed at the completion of capillary condensation
within the framework pores (mid-P/Po N.sub.2 uptake), whereas the
total pore volume (V.sub.t) is the volume adsorbed at 0.99 P/Po.
The textural pore volume (V.sub.tx) is the difference (V.sub.t-V.sub.f).
Pore wall thickness for disordered pore oxides is determined by
subtracting the Horvath-Kawazoe (HK) pore size from the pore-pore
correlation distance determined from x-ray scattering. Pore wall
thickness for periodically ordered pore oxides is determined by
subtracting the Horvath-Kawazoe (HK) pore size from the unit cell
parameter, a.sub.o, determined from x-ray scattering.
[0113] TEM images were obtained on a JEOL JEM-100CXT.TM. II electron
microscope (JEOL, USA, Peabody, Mass.) with a CeB.sub.6 filament
on accelerating voltage of 120 KV, a beam size of approx. 5 .mu.m
and objective lens aperture of 20 .mu.m. Samples were prepared by
sonicating the powdered sample for 20 minutes in ETOH, and then
evaporating 2 drops onto carbon coated copper grids. The electron
diffraction patterns were recorded by using an acceleration voltage
of 120 kV, a beam size of approx. 5 .mu.m, and a diffraction aperture
of 20 .mu.m.
[0114] The thermogravimetric analyses (TGA) of all samples were
performed on a CAHN system TG analyzer using heating rate of 5.degree.
C./min to a maximum value of 1000.degree. C.
[0115] .sup.29Si MAS NMR spectrums were recorded on a Varian VXR-400.TM.
(Palo alto, Calif.) solid-state NMR Spectrometer at 79.5 MHz under
single pulse mode with a 7-mm Zirconia rotor, a spinning frequency
of 4 kHz, pulse width of 8.5 .mu.s and a pulse delay of 800 seconds.
The chemical shifts were externally referenced to Talc (-98.1 ppm).
[0116] .sup.27Al MAS NMR spectra were obtained using a VARIAN VXR-400.TM.
(Palo Alto, Calif.) NMR spectrometer equipped with a VARIAN MAS
probe and Zirconia rotor. The spectrometer frequency was 104.22
Mhz pulse width 2 ms, pulse delay of 1 s, and sample spinning rate
4000 Hz.
[0117] Alumina-substituted and other metal-substituted derivatives
of the mesoporous silicas of the invention are preferably made by
(a) direct assembly, or (b) post-synthesis treatment of a mesoporous
silica with an aluminum or other metal ion reagent. Organo-functionalized
derivatives of silicas can be prepared directly or by post-synthesis
treatment of the silica with organosilane reagents.
[0118] In a typical synthesis of the silica compositions of this
invention, the surfactant and an amount of acid equivalent to the
hydroxide content of the basic silicate solution (e.g., 27% SiO.sub.2
14% NaOH) are mixed at ambient temperature and then added to the
basic silicate to form a reactive silica in the presence of the
structure directing surfactant. This allows for the assembly of
the framework under slightly alkaline pH conditions. The assembly
process continues at the desired temperature for a period of 10
to 20 hours. The surfactant is then removed from the washed and
air-dried products either by solvent extraction with hot ethanol
acid extraction or by calcination in air at 600.degree. C.
1 Materials List Silica sources: Aldrich (Milwaukee, WI) Sodium
Silicate, 27% SiO.sub.2 14% NaOH from Aldrich. Ludox Colloidal,
Ludox HS-40 39.5% SiO.sub.2 0.5% NaOH from Dupont via Aldrich
Aldrich (Milwaukee, WI) Fumed Silica, 99.5% SiO.sub.2 P.Q. Corp
(Valley Forge, PA) Silicas D Sodium Silicate, 29% SiO.sub.2 19%
NaOH RU Sodium silicate, 34% SiO.sub.2 18% NaOH K Sodium Silicate,
32% SiO.sub.2 14% NaOH N Sodium Silicate, 28% SiO.sub.2 12% NaOH
Surfactant Templates: Surfactant specifications:
[0119] The neutral organic amine surfactants include those of the
general formula R.sub.1R.sub.2R.sub.3N in which at least one of
R.sub.1R.sub.2R.sub.3 group is preferably a hydrophobic group.
The remainder of the R.sub.1R.sub.2R.sub.3 group being selected
from various groups.
[0120] The neutral organic polyamine surfactants include those
of the general formula 2
[0121] in which at least one of R.sub.1 to R.sub.5 is preferably
a hydrophobic.
[0122] R.sub.1 is a hydrophobic group preferably containing 6 to
36 carbon atoms;
[0123] R.sub.2 R.sub.4 R.sub.5 are alkyl or aryl groups or hydrogen;
[0124] R.sub.3 is an organic linker group containing one to six
carbon atoms; and x is 0 to 6.
[0125] Acidified, or protonated amine surfactants include those
of the previous general formulas, R.sub.1R.sub.2R.sub.3N and R.sub.1R.sub.2(NR.sub.3).sub.xNR.sub.4R.sub.5
in which an additional proton is temporarily associated with the
basic amine creating a labile cationic charge.
[0126] Aliphatic and aryl amines including polyamines, most preferably
in which one hydrophobic segment contains 6 to 36 carbon atoms.
Specific examples include:
2 DDA Dodecylamine, C.sub.12H.sub.25NH.sub.2 from Aldrich Tallow
Amines from Tomah Industries (Milton, WI). TA Tallow Amine, C.sub.14-18NH.sub.2
TDA Tallow Diamine, C.sub.14-18NH(CH.sub.2).sub.3NH.sub.2 TTA Tallow
Triamine, C.sub.14-18NH(CH.sub.2).sub.3NH(CH.sub.2).sub.3NH.sub.2
TTeA Tallow Tetraamine, C.sub.14-18NH(CH.sub.2).sub.3NH(CH.sub.2).sub-
.3NH(CH.sub.2).sub.3NH.sub.2
[0127] where C.sub.14-18 designates the carbon number of the hydrophobic
hydrocarbon chain attached to polar amine head group of the surfactant.
[0128] Acids:
[0129] HX where X=Cl, Br, I
[0130] H.sub.xY where Y=SO.sup.2-.sub.4 NO.sup.-.sub.3 CO.sup.2-.sub.3
PO.sup.3-.sub.4 and x equals the charge on Y.
[0131] HZ where Z=organic carboxylate, phenolate citrate, glucolate.
EXAMPLE 1
[0132] Example 1 demonstrates the ability to form mesoporous silica
with stable hybrid lamellar and wormhole framework pore structures
from water-soluble silicate and primary amine surfactants. The surfactant
solution was prepared by adding 0.58 gram of dodecylamine (C.sub.12H.sub.25NH.sub.2
DDA) to 10 milliliters of H.sub.2O. 10 milliliters of 1.0 M acetic
acid was added to the surfactant solution and stirred for 10 minutes.
A 2.7-gram quantity of sodium silicate (27% SiO.sub.2 .about.14%
NaOH) in 30 milliliters of water was added to the surfactant-acid
mixture. The reaction vessel was sealed and stirred at room temperature
for 20 hours. The reaction stoichiometry expressed in terms of moles
per mole SiO.sub.2 corresponded to the following:
[0133] 0.25 DDA
[0134] 0.77 NaOH
[0135] 0.80 CH.sub.3O.sub.2H
[0136] 230 H.sub.2O
[0137] The resulting solid product was recovered by filtration
and calcined at 600.degree. C. for 4 hours in air to remove the
incorporated template.
[0138] The X-ray diffraction pattern of the calcined product (FIG.
1) exhibited an intense peak at 3.5 nm and a broad shoulder between
4-6 degrees (2.theta.). The shoulder arises due to scattering from
a wormhole pore topology and not from a broadening of higher order
Bragg reflections of a long-range ordered material. This characteristic
of scattering is not apparent from prior art synthesized mesostructured
materials. A value of 3.5 nm was obtained for the average pore-pore
correlation distance from the initial XRD peak, signifying a very
uniform spatial separation of pores within the oxide matrix. The
N.sub.2 adsorption-desorption isotherm of the calcined product (FIG.
2) exhibited a step-like N.sub.2 adsorption uptake at P/Po 0.15-0.30
and again at P/Po>0.9 indicating capillary condensation within
both framework confined mesopores and intra-particle textural pores,
respectively.
[0139] TEM images of the calcined product (FIGS. 3A and 3B) show
small mesostructured grains. The existence of intra-particle or
textural pores as deduced by N.sub.2 adsorption is clearly seen
in FIG. 4A as the pores formed between the grains of the mesostructured
silicas as these grains aggregate and intergrow into a sponge-like
particle. Evident within the grains is the disordered mesoporous
channel structure and the curved nature of the wormhole channel
topology. The uniform pore to pore correlation distance of these
wormhole pores as seen in TEM are in agreement of values determined
by powder X-ray diffraction (FIG. 1). Additionally, superimposed
upon the disordered wormhole framework structure, and observable
through TEM imaging, is a distinguishing lamellar structure indicated
by arrows in FIGS. 3A and 3B. These molecular sieves with hybrid
lamellar and wormhole pore structure are distinct compositions.
These compositions are only attainable through the current process
using neutral mesostructure assembly of water-soluble silicates
by aliphatic amine surfactants.
COMPARATIVE EXAMPLE 2
[0140] Example 2 demonstrates the ability to form end member mesoporous
silica with a lamellar structure from water-soluble silicate and
aliphatic amine surfactants through control of interfacial surfactant-silica
interactions. This example reveals the dependence of mesophase formation
on H-bonding between surfactant and the neutralized silicate, and
the control of this H-bonding by controlling assembly pH. The surfactant
solution was prepared by adding 0.58 gram of dodecylamine (C.sub.12H.sub.25NH.sub.2
DDA) to 10 milliliters of H.sub.2O. Ten milliliters of 0.25 M acetic
acid was added to the surfactant solution and stirred for 10 minutes.
A 2.7-g quantity of sodium silicate (27% SiO.sub.2 .about.14% NaOH)
in 30 milliliters of water was added to the surfactant-acid mixture.
The reaction mixture at a pH above about 12 was stirred at room
temperature for 20 hours in a sealed reaction vessel. The reaction
stoichiometry expressed in terms of moles per mole SiO.sub.2 corresponded
to the following:
[0141] 0.25 DDA
[0142] 0.77 NaOH
[0143] 0.20 CH.sub.3O.sub.2H
[0144] 230 H.sub.2O
[0145] The resulting solid product was recovered by filtration
and calcined at 600.degree. C. for 4 hours in air to remove the
incorporated template.
[0146] The X-ray diffraction patterns of the as-made product synthesized
under high pH conditions (FIG. 4) exhibits a lamellar pattern with
d.sub.001=4.4 nm. Although this structure is not stable to the removal
of template and undergoes collapse upon calcination, the end member
lamellar structure is clearly identifiable. This example illustrates
that the formation of the framework mesophase is directly related
to the ability of the reactive silica to H-bond the organic structure
director. At high pH values (>10.0) the silicate wall contains
significant negative charge. The counter ions needed to match this
negative charge interfere in the H-bonding between the inorganic
and organic arrays resulting in a mesophase of little or no surface
curvature and the resulting lamellar mesophase. This interaction
is not apparent from the prior art synthetic strategies. Direct
control of the pH of the system, and, therefore indirect control
of the H-bonding interactions at the organic-inorganic interface,
results in a structure directing interface with a variable surface
curvature and, consequently, formation of hybrid structures with
variable mesophases unique to this methodology.
EXAMPLES 3-5
[0147] The following examples indicate the suitability of long
alkyl chain polyamine surfactants as the structure directing surfactant
in the synthesis of silicas with hybrid lamellar and wormhole mesophases.
Additionally, these surfactants can be combined with low cost mineral
or oxy acids for neutralizing the NaOH content of the sodium silicate
starting solution.
[0148] The following tallow amines were obtained from Tomah Industries:
3 TDA Tallow Diamine, C.sub.14-18NH(CH.sub.2).sub.3NH.su- b.2..about.MW
298 g/mole TTA Tallow Triamine, C.sub.14-18NH(CH.sub.2).sub.3NH(CH.sub.2).sub.3NH.sub.2
.about.MW 355 g/mole TTeA Tallow Tetraamine, MW .about.412 g/mole
C.sub.14-18NH(CH.sub.2).sub.3NH(CH.sub.2).sub.3NH(CH.sub.2).sub.-
3NH.sub.2.
[0149] The designation C.sub.14-18 indicates the carbon number
range of the hydrocarbon chain attached to the head group of each
surfactant.
[0150] An appropriate amount of tallow amine surfactant (see Table
1) was added to 5 ml of EtOH, as a co-surfactant. A 10-ml quantity
of 1.0 M HCl was added to the surfactant/EtOH solution while stirring.
25 ml of H.sub.2O was then added to surfactant-acid solution (Solution
A). A 2.8-g quantity of sodium silicate (27% SiO.sub.2 .about.14%
NaOH) was added to 10 ml H.sub.2O (Solution B) Solution B was added
to solution A dropwise while stirring. The reaction vessel was sealed
and stirred at ambient temperature for 20 hours. The reaction stoichiometry
expressed in terms of moles per mole SiO.sub.2 corresponded to the
following:
[0151] 0.20 moles TDA, TTA, or TteA
[0152] 198.0 moles H.sub.2O
[0153] 6.80 moles EtOH
[0154] 0.79 moles HCl
[0155] 0.79 moles NaOH
[0156] The resulting solid products were recovered by filtration.
The surfactant was removed from mesostructured silica by calcination
at 600.degree. C. for 4 hours.
4TABLE 1 Amount of Example Template Template (g) d.sub.100 HK BET
3 TDA 0.751 4.6 4.3 977 4 TTA 0.845 4.6 3.7 1063 5 TTeA 1.038 4.7
4.3 998
[0157] The X-ray diffraction pattern of the calcined product of
Example 3 (FIG. 5) exhibited an intense peak at 4.6 nm and a broad
shoulder between 3-4 degrees (2.theta.). As in Example 1 the X-ray
diffraction pattern indicated a disordered framework pore structure.
The significant intensity of both the primary peak and that of the
shoulder results from the uniformity of the framework pores. The
shoulder arises due to scattering from a wormhole pore topology,
and not from a broadening of higher order Bragg reflections of a
long-range ordered material. This scattering behavior is not apparent
from prior art synthesized mesostructured materials. The N.sub.2
adsorption-desorption isotherm of the calcined product of Example
3 (FIG. 6) shows step-like N.sub.2 adsorption uptakes at P/Po=0.40-0.50
and >0.9 indicating capillary condensation within framework
confined mesopores and intra-particle textural pores, respectively.
[0158] TEM images (FIGS. 8A and 8B) confirmed both the disorder
of the framework pore channels indicated by powder X-ray diffraction
and uniformity of the pore diameters seen in N.sub.2 adsorption.
In addition, the images show the presence of small grained mesostructured
silicas that have aggregated and intergrown into a sponge-like particle
with significant intra-particle textural pore volume. Observable
in the TEM images is the presence of a wormhole pore topology. As
in Example 1 there are areas within the TEM images, FIG. 8A (arrow),
which indicate the presence of a lamellar mesostructure. Again,
this hybrid lamellar and wormhole structure is unique to the current
methodology.
EXAMPLES 6-9
[0159] The following examples are chosen to illustrate the use
of different silica sources with a wide range of SiO.sub.2 to alkali
metal (Na.sup.+) hydroxide ratios as precursors to mesoporous materials
assembled through H-bonding interactions with aliphatic amine surfactant
structure directors. With increasing ratio of SiO.sub.2/Na.sub.2O,
the pH of the silicate source decreases, yet the silicate species
increases in polymeric size. The silica sources were provided by
P.Q. Corporation (Valley Forge, Pa.) and used according to the grade
indicated by the supplier (see Table 2).
5TABLE 2 Silicate Wt. % SiO.sub.2/ Example Grade SiO.sub.2 Na.sub.2O
6 D 29.5 2.06 7 RU 33.7 2.51 8 K 32.2 3.02 9 N 28.4 3.29
[0160] A 0.750-g quantity of TDA was added to 5 mL of EtOH. Molar
quantities of HCl equal to the NaOH content of each silicate solution
grade was added to the surfactant solution along with 35 mL of H.sub.2O
(Solution A). An appropriate amount of the silicate source (Table
3) was added to 10 mL of H.sub.2O (Solution B). Solution B was added
to solution A dropwise while stirring. The reaction stoichiometry
expressed in terms of moles per mole SiO.sub.2 corresponded to the
values given in Table 3.
6 TABLE 3 Mass SiO.sub.2 Stoichiometry/mole SiO.sub.2 Example Brand
(g) TDA H.sub.2O EtOH NaOH HCl 6 D 2.56 0.20 198 6.8 0.97 0.97 7
RU 2.24 0.20 198 6.8 0.79 0.79 8 K 2.35 0.20 198 6.8 0.66 0.66 9
N 2.66 0.20 198 6.8 0.61 0.61
[0161] The reaction vessels were sealed and shaken at 240 rpm for
20 hours at 45.degree. C. The products were recovered by filtration,
washed and air-dried at ambient temperatures for 24 hours. The products
then were calcined at 600.degree. C. for 4 hours in order to remove
the incorporated template.
7 TABLE 4 HK (nm) BET (m.sup.2/g) Example d.sub.100 nm Pore Size
Surface area 6 4.8 4.9 949 7 4.8 4.9 916 8 4.7 4.8 793 9 4.9 4.8
877
[0162] Table 4 lists the physico-chemical properties for Examples
6 to 9. Regardless of the NaOH to SiO.sub.2 ratio of the silicate
source, the mesopore structure formed by this procedure remained
virtually identical to Example 3. In each of the examples, independent
of ratio, the structures were very similar in pore diameter, pore
to pore spacing and BET surface area. Each sample exhibited powder
X-ray diffraction patterns similar to FIG. 5 N.sub.2 adsorption
desorption isotherms as seen in FIG. 6 and TEM images similar to
those in FIG. 7.
[0163] With increasing ratio of SiO.sub.2/Na.sub.2O, the pH of
silicate source decreases, yet the silicate oligomers increase in
size. Neutralization of the silicate source with equal molar amounts
of acid, regardless of the total hydroxide concentration and oligomeric
size, results in a silica that is efficiently structured into a
stable hybrid wormhole topology.
EXAMPLES 10 AND 11
[0164] Examples 10 and 11 demonstrate the ability to form hybrid
lamellar and wormhole mesoporous silica from water-soluble silicate
and aliphatic diamine surfactants through control of interfacial
interactions. This example reveals the dependence of mesophase formation
on H-bonding between surfactant and neutralized silicate and a method
of controlling this H-bonding by controlling the assembly temperature.
The following examples demonstrate that increasing the assembly
temperature increases the framework pore diameter, along with increasing
the inorganic crosslinking within the silicate wall structure. This
structural behavior is not apparent from prior art and is a characteristic
property of the current H-bonding assembly mechanism.
[0165] A 0.750-g amount of TDA was added to 5 mL of EtOH. A 10-ml
amount of 1.0 M HCl was added to the surfactant/EtOH solution while
stirring. 25 ml of H.sub.2O then was added to the solution (Solution
A). A 2.8-g amount of sodium silicate (27% SiO.sub.2 .about.14%
NaOH) was added to 10 ml H.sub.2O (solution B). Solution B was added
to solution A dropwise while stirring. The reaction stoichiometry
expressed in terms of moles per mole SiO.sub.2 corresponded to the
following:
[0166] 0.20 moles TDA
[0167] 198.0 moles H.sub.2O
[0168] 6.80 moles EtOH
[0169] 0.79 moles HCl
[0170] 0.79 moles NaOH
[0171] The resulting gels were stirred at 45.degree. C. (Example
11) or 65.degree. C. (Example 12) for 20 hours to obtain products.
The resulting solid products were recovered by filtration and calcined
at 600.degree. C. for 4 hours in air to remove the incorporated
template.
8TABLE 5 EK BET pore surface Example .degree. C. d.sub.100 size
area Q.sup.4/(Q.sup.3 + Q.sup.2) 3 Ambient 4.6 4.3 1063 2.1 11 45.degree.
C. 4.9 4.8 906 3.2 12 65.degree. C. 5.1 5.4 754 3.8
[0172] Table 5 lists the physico-chemical properties for Examples
3 11 and 12. Clearly, increasing the synthesis temperature has
a profound affect on the Horvath-Kawazoe (HK) mesopore diameter.
As the temperature increases, the pore diameter assembled by the
polyamine surfactant systematically increases from approximately
4.3 to 5.4 nm and the surface area decreases from 1063 to 754 m.sup.2/g.
Also the framework crosslinking parameter Q.sup.4/(Q.sup.3+Q.sup.2)
increases with increasing assembly temperature. Each sample exhibits
powder X-ray diffraction patterns similar to FIG. 5 N.sub.2 adsorption
desorption isotherms as seen in FIG. 6 and TEM images similar to
those in FIGS. 7A and 7B.
[0173] The increasing diameter of the framework pore structure
is initiated by a temperature-induced decrease in H-bonding at the
interface. The decreasing degree of H-bonding is due to the increased
thermal energy at the surfactant-silica interface, combined with
the deceasing silanols present at the interface for H-bonding with
the amine. Consequently, the decrease in H-bonding results in a
decreasing surface curvature of the organic micelle-inorganic interface.
Additionally, the deceasing H-bonding between silica and surfactant
causes the surfactant micelle to undergo a self-swelling process
in which the non-H-bonded surfactant penetrates the core of the
micelle. The decreasing surface curvature of the interface combined
with the self-swelling of the micelle results in the significant
increase in pore diameter with increasing temperature. This structural
behavior is not apparent from prior art and is a characteristic
property of the current H-bonding assembly mechanism.
[0174] As determined by .sup.29Si MAS NMR spectroscopy, increasing
the synthesis temperature increases the degree on silica condensation,
reducing the silanols present in the silica framework and increasing
the degree of silica framework cross-linking. The extent of the
cross-linking of the silica wall structure is quantified by the
ratio of fully cross-linked Q.sup.4 silica sites (.about.-110 ppm)
to incompletely cross-linked silica sites (Q.sup.3 .about.-98 ppm,
Q.sup.2 .about.-90 ppm). As is seen in Table 5 the ratio of Q.sup.4/(Q.sup.3+Q.sup.2)
increases 81% from 2.1 to 3.8 with increasing synthesis temperature
from ambient (.about.20.degree. C.) to 65.degree. C.
EXAMPLE 13
[0175] The following example is selected to stress the ability
to remove the surfactant from the pore structure by a straightforward
solvent extraction. Additionally, simple removal of the surfactant
by solvent extraction further confirms the existence of solely H-bonding
between the surfactant and silica wall structure.
[0176] (Product A) A 0.04-g quantity of the air-dried and non-calcined
product of Example 3 was subjected to thermogravimetric analysis
(TGA) at a heating rate of 5.degree. C./minute. The total weight
loss of this sample was approximately 53%. Four distinguishable
weight loss steps were centered at temperatures of 40.degree. C.,
187.degree. C., 290.degree. C. and 540.degree. C. which could be
attributed to the loss of excess H.sub.2O, adsorbed pore H.sub.2O,
desorption or decomposition of template, and de-hydroxylation of
the silicate surface, respectively.
[0177] (Product B) One gram of the air-dried and non-calcined product
of Example 3 was mixed with 100 mL of EtOH and refluxed while stirring
for 1 hour. Product was filtered, washed with another portion of
EtOH. The above washing procedure was repeated twice and the filtered
product was air-dried for 24 hours at ambient temperature. 0.04
grams of product B was subjected to TGA analysis. In contrast to
product A, product B reveals only a 17% total weight loss with 14%
corresponding to H.sub.2O desorption and de-hydroxylation. Analysis
of the two samples shows that more than 85% of the surfactant amine
has been removed from the mesostructure with this simple alcohol
extraction procedure. The mesostructure retains its x-ray diffraction
pattern with relative intensity greater than that of the surfactant
occluded sample. This shows that the neutral amine surfactant has
been removed from the neutral framework of the inorganic compositions
by ethanol extraction. The extracted organic template in the form
of EtOH solution can be recycled and reused after simple concentration
of the solution. In order to confirm the thermal stability of the
extracted product B, calcination was performed in air at 600.degree.
C. for 7 hours. The X-ray analysis of the calcined product shows
that the correlation distance is retained even after prolonged calcination.
EXAMPLE 14
[0178] Mesoporous silica from Example 3 were synthesized to have
varying amounts of alkali metal present in the calcined materials.
All metal ions can be removed from the product with thorough washing
of the material in H.sub.2O as determined from Inductively Coupled
Plasma (ICP) analysis.
EXAMPLE 15
[0179] The following example uses a polyamine surfactants as the
structure directing surfactant in the assembly of a hybrid wormhole
and hexagonally ordered molecular sieve silicas. As in previous
hybrid structures Examples 1 and 3 the degree of curvature at the
organic micelle-inorganic interface is variable and, therefore,
controllable through H-bonding interactions unique to the present
methodology. The amine surfactant used in preparing these compositions
was
[0180] TTeA Tallow Tetraamine, MW .about.412 g/mole C.sub.14-18NH(CH.sub.2).sub.3NH(CH.sub.2).sub.3NH(CH.sub.2).sub.3NH.sub.2
[0181] A 1.038-g quantity of tallow tetraamine surfactant (TTeA)
was added to 5 ml of EtOH. A 12 ml volume of 1.0 M HCl was added
to the surfactant/EtOH solution while stirring. 25 ml of H.sub.2O
then was added to the surfactant-acid solution (Solution A). 2.8
g of sodium silicate (27% SiO.sub.2 .about.14% NaOH) was added
to 10 ml H.sub.2O (Solution B). Solution B was added to solution
A dropwise while stirring, reaction vessel sealed and stirred at
45.degree. C. for 20 hours. The reaction stoichiometry expressed
in terms of moles per mole SiO.sub.2 corresponded to the following:
[0182] 0.20 moles TTeA
[0183] 198.0 moles H.sub.2O
[0184] 6.80 moles EtOH
[0185] 0.95 moles HCl
[0186] 0.79 moles NaOH
[0187] The resulting solid products were recovered by filtration.
Surfactant was removed from mesostructured silica by calcination
at 600.degree. C. for 4 hours.
9 TABLE 6 Amount of Template .sup.d100 HK BET Example Template
(g) (nm) (nm) m.sup.2/g 15 TTeA 1.038 4.7 4.2 940
[0188] The X-ray diffraction pattern of the calcined product of
Example 15 exhibited an intense peak at 4.7 nm and a resolved second
peak between 3-4 degrees (20) (FIG. 5). Unlike Example 5 the resolved
second peak in the X-ray diffraction pattern indicates a small domain
hexagonally ordered framework pore structure. TEM images (FIGS.
8A and 8B) and selected area electron diffraction (FIG. 10C) confirm
the hexagonal order of the pore channels with very small domain
sizes. The ordered domains are clearly observed in the TEM images,
although there exists a significant fraction of the pore structure
resembling a wormhole structure as seen in FIGS. 8A and 8B. There
exists no clear phase boundary between the ordered and disordered
mesopore phases. The N.sub.2 adsorption-desorption isotherm of the
calcined product of Example 15 (see FIG. 6 Table 6) shows step-like
N.sub.2 adsorption uptakes at P/Po=0.40-0.50 and >0.9 indicating
capillary condensation within uniform framework confined mesopores
and extra-particle textural pores, respectively.
EXAMPLE 16
[0189] The following example indicates the ability to directly
substitute hetero-atoms, such as aluminum, into the silica framework
of these hybrid silica framework mesostructures using basic (pH>7)
reagent conditions using a polyamine surfactant as the structure
director.
[0190] TDA Tallow Diamine, C.sub.14-18NH(CH.sub.2).sub.3NH.sub.2
where C.sub.14-18 indicates the range of carbon atoms in the hydrophobic
chain, .about.MW 298 g/mole
[0191] TDA (0.75 g) was added to 5 mL of ethanol. A 10-mL portion
of 1.0 M HCl in 25 mL of H.sub.2O was then added to yield acidified
amine solution (Solution A). A 2.7-g quantity of sodium silicate
(27% SiO.sub.2 .about.14% NaOH, Aldrich) and 0.067 g of NaAlO.sub.2.H.sub.2O
was added to 10 M1 H.sub.2O and stirred for 10 min (Solution B).
Solution B was added to solution A dropwise while stirring. The
reaction vessel was sealed and stirred at ambient temperature for
20 hours. The reaction stoichiometry expressed in terms of moles
per mole Si/Al corresponded to the following:
[0192] 0.20 moles TDA
[0193] 6.80 moles EtOH
[0194] 0.79 moles HCl
[0195] 0.79 moles NaOH
[0196] Si/Al=20 SiO.sub.2/Al.sub.2O.sub.3=40
[0197] The resulting solid products were recovered by filtration.
Surfactant was removed from mesostructured silica by calcination
at 600.degree. C. for 4 hours.
[0198] The X-ray diffraction pattern of the calcined product of
Example 16 was similar to that seen in FIG. 6 and exhibited an intense
peak at 4.6 nm and a broad shoulder between 3-4 degrees (2). As
in Example 3 the X-ray diffraction pattern indicated a disordered
framework pore structure. The significant intensity of both the
primary peak and that of the shoulder results from the uniformity
of the pores and their spacing.
[0199] The N.sub.2 adsorption-desorption isotherm of the calcined
product of Example 16 are also similar to those of Example 3 (FIG.
7) and showed N.sub.2 adsorption uptakes at P/Po 0.40-0.50 and >0.9
indicating capillary condensation within framework confined mesopores
and intra-particle textural pores respectively.
[0200] The TEM images were similar to those shown in FIGS. 8A and
8B and confirmed both the disorder of the pore channels indicated
by powder X-ray diffraction and the uniformity of the pore diameters
seen in N.sub.2 adsorption. They also confirmed the presence of
small grained mesostructured silicas that aggregate and intergrow
into a sponge-like particle with significant intra-particle textural
pore volume. Observable in the TEM images was the presence of a
wormhole pore topology.
[0201] Elemental analysis confirms the Si/Al value equal to 20.
EXAMPLE 17
[0202] The following example indicated the ability to directly
substitute hetero-atoms, such as aluminum, into the silica framework
of these hybrid silica framework mesostructures using acidic (pH<7)
reagent conditions and a polyamine surfactant as the structure-directing
agent.
[0203] TDA Tallow Diamine, C.sub.14-18NH(CH.sub.2).sub.3NH.sub.2
where C.sub.14-18 indicates the range of carbon atoms in the hydrophobic
chain, .about.MW 298 g/mole
[0204] TDA (0.75 g) was added to 5 mL of ethanol. A 8-mL quantity
of 1.0 M HCl in 25 mL of H.sub.2O was then added along with 0.24
g of Al(NO.sub.3).sub.3.9H.sub.2O to yield an acidified amine/Al.sup.+3
solution (Solution A). A 2.7-g quantity of sodium silicate (27%
SiO.sub.2 .about.14% NaOH, Aldrich) was added to 10 ml H.sub.2O
and stirred for 10 minutes (Solution B). Solution B was added to
solution A dropwise while stirring. The reaction vessel was sealed
and the mixture was stirred at ambient temperature for 20 hours.
The reaction stoichiometry expressed in terms of moles per mole
Si/Al corresponded to the following:
[0205] 0.20 moles TDA
[0206] 198.0 moles H.sub.2O
[0207] 6.80 moles EtOH
[0208] 0.79 moles HCl
[0209] 0.79 moles NaOH
[0210] Si/Al=20 SiO.sub.2/Al.sub.2O.sub.3=40
[0211] The resulting solid products were recovered by filtration.
Surfactant was removed from mesostructured alumina-silica by calcination
at 600.degree. C. for 4 hours.
[0212] The X-ray diffraction pattern of the calcined product of
Example 17 is similar to that seen in FIG. 6 and exhibits an intense
peak at low angle (2.theta.) and a broad shoulder at higher angles
(2). As in Example 16 the X-ray diffraction pattern indicates a
disordered framework pore structure. The significant intensity of
both the primary peak and that of the shoulder results from the
uniformity of the pores and their spacing.
[0213] The N.sub.2 adsorption-desorption isotherm of the calcined
product of Example 17 are also similar to those of Example 16 (FIG.
7) and show N.sub.2 adsorption uptakes at P/Po 0.40-0.50 and >0.9
indicating capillary condensation within framework confined mesopores
and intra-particle textural pores, respectively.
[0214] TEM images were similar to those shown in FIGS. 8A and 8B
and confirmed both the disorder of the pore channels indicated by
powder X-ray diffraction and the uniformity of the pore diameters
seen in N.sub.2 adsorption. They also confirmed the presence of
small grained mesostructured silicas that aggregate and intergrow
into a sponge-like particle with significant intra-particle textural
pore volume. Observable in the TEM images was the presence of a
wormhole pore topology.
[0215] Elemental analysis confirmed the Si/Al value was equal to
20.
EXAMPLE 18
[0216] The following example demonstrates the ability to neutralize
the silicate solution with an acid after mixing the silicate solution
with the non-acidified, or protonated, polyamine solution in the
assembly of hybrid silica framework mesostructures.
[0217] TDA Tallow Diamine, C.sub.14-18NH(CH.sub.2).sub.3NH.sub.2
where C.sub.14-18 indicates the range of carbon atoms in the hydrophobic
chain, .about.MW 298 g/mole
[0218] TDA (0.75 g) added to 5 mL of ethanol. A 25-mL volume of
H.sub.2O was added to yield amine solution(Solution A). A 2.8-g
quantity of sodium silicate (27% SiO.sub.2 .about.14%NaOH, Aldrich)was
added to 10 ml H.sub.2O and stirred for 10 min(Solution B). Solution
B was added to solution A dropwise while stirring. A 10-mL volume
of 1.0 M HCl was added to the silicate-amine solution with stirring.
The reaction vessel was sealed and the reaction mixture was stirred
at ambient temperature for 20 hours. The reaction stoichiometry
expressed in terms of moles per mole SiO.sub.2 correspond to the
following:
[0219] 0.20 moles TDA
[0220] 198.0 moles H.sub.2O
[0221] 6.80 moles EtOH
[0222] 0.79 moles HCl
[0223] 0.79 moles NAOH
[0224] The resulting solid products were recovered by filtration.
The Surfactant was removed from the mesostructured silica by calcination
at 600.degree. C. for 4 hours.
[0225] The X-ray diffraction pattern of the calcined product of
Example 18 was similar to that seen in FIG. 6. As in Example 3
the X-ray diffraction pattern indicated a disordered framework pore
structure. The significant intensity of both the primary peak and
that of the shoulder resulted from the uniformity of the pores and
the spacing of the pores.
[0226] The N.sub.2 adsorption-desorption isotherms of the calcined
product of Example 18 were similar to those of example 3 (FIG. 7)
and showed N.sub.2 adsorption uptakes at P/Po 0.40-0.50 and >0.9
indicating capillary condensation within framework confined mesopores
and intra-particle textural pores, respectively.
[0227] The TEM were similar to those seen in FIGS. 8A and 8B and
confirmed both the disorder of the pore channels indicated by powder
X-ray diffraction and the uniformity of the pore diameters seen
in N.sub.2 adsorption. They also confirmed the presence of small
grained mesostructured silicas that aggregate and intergrow into
a sponge-like particle with significant intra-particle textural
pore volume. Observable in the TEM images was the presence of a
wormhole pore topology.
EXAMPLE 19
[0228] The following example are presented to demonstrate the ability
to assemble hybrid silica framework mesostructures by initially
mixing the silicate and amine solutions at low pH (<4) and then
titrating with a base to raise the pH to the preferred value (6.0-8.5)for
precipitation of the products.
[0229] TDA Tallow Diamine, C.sub.14-18NH(CH.sub.2).sub.3NH.sub.2
where C.sub.14-18 indicates the range of carbon atoms in the hydrophobic
chain, .about.MW 298 g/mole
[0230] TDA (0.75 g) was added to 5 mL of ethanol. A 25-mL volume
of 1.0 M HCl was then added to yield the acidified amine solution(Solution
A). A 2.8-g quantity of sodium silicate (27% SiO.sub.2 .about.14%NaOH,
Aldrich) was added to 10 ml H.sub.2O and stirred for 10 min(Solution
B). Solution B was added to solution A dropwise while stirring.
15 mL of 1.0 M NaOH was added to the silicate-amine solution with
stirring, yielding a final pH of 6.0-8.5. The reaction vessel was
sealed and the mixture was stirred at ambient temperature for 20
hours. The reaction stoichiometry expressed in terms of moles per
mole Si/Al corresponded to the following:
[0231] 0.20 moles TDA
[0232] 198.0 moles H.sub.2O
[0233] 6.80 moles EtOH
[0234] 1.98 moles HCl
[0235] 1.98 moles NaOH
[0236] The resulting solid products were recovered by filtration.
The surfactant was removed from the mesostructured silica by calcination
at 600.degree. C. for 4 hours.
[0237] The X-ray diffraction pattern of the calcined product of
Example 19 was similar to that seen in FIG. 6. As in Example 3
the X-ray diffraction pattern indicated a disordered framework pore
structure. The significant intensity of both the primary peak and
that of the shoulder resulted from the uniformity of the pores and
their spacing.
[0238] The N.sub.2 adsorption-desorption isotherm of the calcined
product of Example 19 were similar to those of example 3 (FIG. 7)
and showed N.sub.2 adsorption uptakes at P/Po 0. 40-0.50 and >0.9
indicative of capillary condensation within framework confined mesopores
and intra-particle textural pores respectively.
[0239] The TEM images were similar to those seen in FIGS. 8A and
8B and confirmed both the disorder of the pore channels indicated
by powder X-ray diffraction and the uniformity of the pore diameters
evidenced by N.sub.2 adsorption. They also confirmed the presence
of small grained mesostructured silicas that aggregate and intergrow
into a sponge-like particle with significant intra-particle textural
pore volume. Observable in the TEM images was the presence of a
wormhole pore topology.
EXAMPLE 20
[0240] The following example is presented to demonstrate the ability
to substitute an organo-silicate solution for an inorganic sodium
silicate solution in the assembly of hybrid silica framework mesostructures.
[0241] TDA Tallow Diamine, C.sub.14-18NH(CH.sub.2).sub.3NH.sub.2
where C.sub.14-18 indicates the range of carbon atoms in the hydrophobic
chain, .about.MW 298 g/mole
[0242] TMAOH Tetramethylammonium hydroxide
[0243] A 0.76-g quantity of fumed silica (Cab-O-Sil) was added
to 15 mL of H.sub.2O and then 2.76 g of TMAOH was added. The mixture
was heated to 40.degree. C. for 72 h (Solution A).
[0244] TDA (0.75 g) was added to 5 mL of ethanol. A 25-mL volume
of 1.0 M HCl and 5 mL of H.sub.2O was added to yield an acidified
amine solution(Solution B). Solution A was added to solution B dropwise
while stirring. The reaction vessel was sealed and stirred at ambient
temperature for 20 hours. The reaction stoichiometry expressed in
terms of moles per mole Si/Al corresponded to the following:
[0245] 0.20 moles TDA
[0246] 198.0 moles H.sub.2O
[0247] 6.80 moles EtOH
[0248] 2.0 moles HCl
[0249] 2.0 moles TMAOH
[0250] The resulting solid products were recovered by filtration.
The surfactant was removed from the mesostructured silica by calcination
at 600.degree. C. for 4 hours.
[0251] The X-ray diffraction pattern of the calcined product of
Example 20 were similar to that seen in FIG. 6. As in Example 3
the X-ray diffraction pattern indicated a disordered framework pore
structure. The significant intensity of both the primary peak and
that of the shoulder results from the uniformity of the pores and
their spacing.
[0252] The N.sub.2 adsorption-desorption isotherm of the calcined
product of Example 20 were similar to those of example 3 (FIG. 7)
and showed N.sub.2 adsorption uptakes at P/Po 0.40-0.50 and >0.9
indicating capillary condensation within framework confined mesopores
and intra-particle textural pores respectively.
[0253] The TEM images were similar to those seen in FIGS. 8A and
8B and confirmed both the disorder of the pore channels indicated
by powder X-ray diffraction and the uniformity of the pore diameters
indicated by N.sub.2 adsorption. They also confirmed the presence
of small grained mesostructured silicas that aggregate and intergrow
into a sponge-like particle with significant intra-particle textural
pore volume. Observable in the TEM images was the presence of a
wormhole pore topology.
[0254] It is intended that the foregoing description be only illustrative
of the present invention and that the present invention be limited
only by the hereinafter appended claims. |