Molecular sieve abstract
The present invention relates to new molecular sieve SSZ-71 prepared
using a N-benzyl-14-diazabicyclo[2.2.2]octane cation as a structure-directing
agent, methods for synthesizing SSZ-71 and processes employing SSZ-71
in a catalyst.
Molecular sieve claims
What is claimed is:
1. A method for performing an acylation reaction on an aromatic
substrate ArH.sub.n to form a product ArH.sub.n-1COR, the method
comprising the steps of: providing the aromatic substrate, intimately
mixing the substrate and an acylating agent, wherein the acylating
agent is selected from the group consisting of a carboxylic acid
derivative, a carboxylic acid, an acid anhydride, an ester, and
an acyl halide, and exposing an intimate mixture thus formed to
a catalyst comprising a molecular sieve produced by the method comprising:
(1) preparing an as-synthesized molecular sieve having a composition,
as synthesized and in the anhydrous state, in terms of mole ratios
as follows: YO.sub.2/WO.sub.d 15 .infin. M.sub.2/n/YO.sub.2 0 0.03
Q/YO.sub.2 0.02 0.05 wherein Y is silicon, germanium or a mixture
thereof; W is zinc, titanium or mixtures thereof; d is 1 or 2 (i.e.,
d is 1 when W is divalent or 2 when W is tetravalent); M is an alkali
metal cation, alkaline earth metal cation or mixtures thereof; n
is the valence of M (i.e., 1 or 2); and Q is a N-benzyl-14-diazabicyclo[2.2.2]octane
cation, the as-synthesized molecular sieve having the X-ray diffraction
lines of Table I; (2) thermally treating the as-synthesized molecular
sieve at a temperature and for a time sufficient to remove the N-benzyl-14-diazabicyclo[2.2.2]octane
cation from the molecular sieve; and (3) optionally, replacing at
least part of the zinc and/or titanium with a metal selected from
the group consisting of aluminum, gallium, iron, boron, indium,
vanadium and mixtures thereof.
2. The method of claim 1 wherein the organic substrate is selected
from the group consisting of benzene, toluene, anisole and 2-naphthol.
3. The method of claim 2 wherein the organic substrate is anisole.
4. The method of claim 1 wherein the acylating agent is selected
from the group consisting of carboxylic acid derivatives, carboxylic
acids, acid anhydrides, esters, and acyl halides.
Molecular sieve description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to new molecular sieve SSZ-71 a
method for preparing SSZ-71 using a N-benzyl-14-diazabicyclo[2.2.2]octane
cation as a structure directing agent and the use of SSZ-71 in catalysts
for, e.g., hydrocarbon conversion reactions.
2. State of the Art
Because of their unique sieving characteristics, as well as their
catalytic properties, crystalline molecular sieves and zeolites
are especially useful in applications such as hydrocarbon conversion,
gas drying and separation. Although many different crystalline molecular
sieves have been disclosed, there is a continuing need for new zeolites
with desirable properties for gas separation and drying, hydrocarbon
and chemical conversions, and other applications. New zeolites may
contain novel internal pore architectures, providing enhanced selectivities
in these processes.
Crystalline aluminosilicates are usually prepared from aqueous
reaction mixtures containing alkali or alkaline earth metal oxides,
silica, and alumina. Crystalline borosilicates are usually prepared
under similar reaction conditions except that boron is used in place
of aluminum. By varying the synthesis conditions and the composition
of the reaction mixture, different zeolites can often be formed.
SUMMARY OF THE INVENTION
The present invention is directed to a family of molecular sieves
with unique properties, referred to herein as "molecular sieve
SSZ-71" or simply "SSZ-71". Preferably, SSZ-71 is
in its silicate, zincosilicate, aluminosilicate, titanosilicate,
germanosilicate, vanadosilicate, ferrosilicate or borosilicate form.
The term "silicate" refers to a molecular sieve having
a high mole ratio of silicon oxide relative to aluminum oxide, preferably
a mole ratio greater than 100 including molecular sieves comprised
entirely of silicon oxide. As used herein, the term "zincosilicate"
refers to a molecular sieve containing both zinc oxide and silicon
oxide. The term "aluminosilicate" refers to a molecular
sieve containing both aluminum oxide and silicon oxide and the term
"borosilicate" refers to a molecular sieve containing
oxides of both boron and silicon.
In accordance with the present invention, there is provided a method
for performing an acylation reaction on an aromatic substrate ArH.sub.n
to form a product ArH.sub.n-1COR, the method comprising the steps
of: providing the aromatic substrate, intimately mixing the substrate
and an acylating agent, wherein the acylating agent is selected
from the group consisting of a carboxylic acid derivative, a carboxylic
acid, an acid anhydride, an ester, and an acyl halide, and exposing
an intimate mixture thus formed to a catalyst comprising a molecular
sieve produced by the method comprising: (1) preparing an as-synthesized
molecular sieve having a composition, as synthesized and in the
anhydrous state, in terms of mole ratios as follows: YO.sub.2/WO.sub.d
15 .infin. M.sub.2/n/YO.sub.2 0 0.03 Q/YO.sub.2 0.02 0.05 wherein
Y is silicon, germanium or a mixture thereof; W is zinc, titanium
or mixtures thereof; d is 1 or 2 (i.e., d is 1 when W is divalent
or 2 when W is tetravalent); M is an alkali metal cation, alkaline
earth metal cation or mixtures thereof; n is the valence of M (i.e.,
1 or 2); and Q is a N-benzyl-14-diazabicyclo[2.2.2]octane cation,
the as-synthesized molecular sieve having the X-ray diffraction
lines of Table I; (2) thermally treating the as-synthesized molecular
sieve at a temperature and for a time sufficient to remove the N-benzyl-14-diazabicyclo[2.2.2]octane
cation from the molecular sieve; and (3) optionally, replacing at
least part of the zinc and/or titanium with a metal selected from
the group consisting of aluminum, gallium, iron, boron, indium,
vanadium and mixtures thereof.
The molecular sieve of the present invention may be predominantly
in the hydrogen form, which hydrogen form is prepared by ion exchanging
with an acid or with a solution of an ammonium salt followed by
a second calcination. If the molecular sieve is synthesized with
a high enough ratio of SDA cation to sodium ion, calcination alone
may be sufficient. For high catalytic activity, the SSZ-71 molecular
sieve may be predominantly in its hydrogen ion form. As used herein,
"predominantly in the hydrogen form" means that, after
calcination, at least 80% of the cation sites are occupied by hydrogen
ions and/or rare earth ions. It should be noted that the mole ratio
of the first oxide or mixture of first oxides to the second oxide
can be infinity, i.e., there is no second oxide in the molecular
sieve. In these cases, the molecular sieve is an all-silica molecular
sieve or a germanosilicate.
DETAILED DESCRIPTION OF THE INVENTION
The present invention comprises a family of molecular sieves designated
herein "molecular sieve SSZ-71" or simply "SSZ-71".
In preparing SSZ-71 a N-benzyl-14-diazabicyclo[2.2.2]octane cation
(referred to herein as "benzyl DABCO") is used as a structure
directing agent ("SDA"), also known as a crystallization
template. The SDA useful for making SSZ-71 has the following structure:
##STR00001##
The SDA cation is associated with an anion (X.sup.-) which may
be any anion that is not detrimental to the formation of the molecular
sieve. Representative anions include halogen, e.g., fluoride, chloride,
bromide and iodide, hydroxide, acetate, sulfate, tetrafluoroborate,
carboxylate, and the like. Hydroxide is the most preferred anion.
Benzyl DABCO and a method for making it are disclosed in U.S. Pat.
No. 5653956 issued Aug. 5 1997 to Zones.
SSZ-71 is prepared from a reaction mixture having the composition
shown in Table A below.
TABLE-US-00001 TABLE A Reaction Mixture Typical Preferred YO.sub.2/WO.sub.d
>15 >30 OH--/YO.sub.2 0.10 0.50 0.20 0.30 Q/YO.sub.2 0.05
0.50 0.10 0.20 M.sub.2/n/YO.sub.2 0 0.40 0.10 0.25 H.sub.2O/YO.sub.2
10 80 15 45
where Y is silicon, germanium or a mixture thereof; W is zinc,
titanium or mixtures thereof; d is 1 or 2 (i.e., d is 1 when W is
divalent or 2 when W is tetravalent); M is an alkali metal cation,
alkaline earth metal cation or mixtures thereof; n is the valence
of M (i.e., 1 or 2); and Q is a N-benzyl-14-diazabicyclo[2.2.2]octane
cation.
In practice, SSZ-71 is prepared by a process comprising:
(a) preparing an aqueous solution containing sources of at least
one oxide capable of forming a molecular sieve and a benzyl DABCO
cation having an anionic counterion which is not detrimental to
the formation of SSZ-71;
(b) maintaining the aqueous solution under conditions sufficient
to form SSZ-71; and
(c) recovering the SSZ-71.
SSZ-71 can be prepared as a zincosilicate or titanosilicate. However,
once the SSZ-71 is made, the zinc and/or titanium can be replaced
with other metals by techniques well known in the art. Accordingly,
SSZ-71 may comprise the molecular sieve and the SDA in combination
with metallic and non-metallic oxides bonded in tetrahedral coordination
through shared oxygen atoms to form a cross-linked three dimensional
crystal structure. The metallic and non-metallic oxides comprise
one or a combination of oxides of (1) a first tetravalent element(s),
and (2) one or a combination of a divalent element(s), trivalent
element(s), pentavalent element(s), second tetravalent element(s)
different from the first tetravalent element(s) or mixture thereof.
The first tetravalent element(s) is preferably selected from the
group consisting of silicon, germanium and combinations thereof.
More preferably, the first tetravalent element is silicon. The divalent
element, trivalent element, pentavalent element and second tetravalent
element (which is different from the first tetravalent element)
is preferably selected from the group consisting of zinc, aluminum,
gallium, iron, boron, titanium, indium, vanadium and combinations
thereof. More preferably, the divalent or trivalent element or second
tetravalent element is zinc, aluminum, titanium or boron.
Silicon can be added as silicon oxide or Si(OC.sub.2H.sub.5).sub.4.
Zinc can be added as a zinc salt such as zinc acetate. Titanium
can be added as Ti(OC.sub.2H.sub.5).sub.4.
A source zeolite reagent may provide a source of metals. In most
cases, the source zeolite also provides a source of silica. The
source zeolite may also be used as a source of silica, with additional
silicon added using, for example, the conventional sources listed
above. Use of a source zeolite reagent is described in U.S. Pat.
No. 5225179 issued Jul. 6 1993 to Nakagawa entitled "Method
of Making Molecular Sieves", the disclosure of which is incorporated
herein by reference.
Typically, an alkali metal hydroxide and/or an alkaline earth metal
hydroxide, such as the hydroxide of sodium, potassium, lithium,
cesium, rubidium, calcium, strontium, barium and magnesium, is used
in the reaction mixture; however, this component can be omitted
so long as the equivalent basicity is maintained. The SDA may be
used to provide hydroxide ion. Thus, it may be beneficial to ion
exchange, for example, the halide to hydroxide ion, thereby reducing
or eliminating the alkali metal hydroxide quantity required. The
alkali metal cation or alkaline earth cation may be part of the
as-synthesized material, in order to balance valence electron charges
therein.
The reaction mixture is maintained at an elevated temperature until
the crystals of the SSZ-71 are formed. The hydrothermal crystallization
is usually conducted under autogenous pressure, at a temperature
between 100.degree. C. and 200.degree. C., preferably between 135.degree.
C. and 160.degree. C. The crystallization period is typically greater
than 1 day and preferably from about 3 days to about 20 days.
Optionally, the molecular sieve is prepared using mild stirring
or agitation.
During the hydrothermal crystallization step, the SSZ-71 crystals
can be allowed to nucleate spontaneously from the reaction mixture.
The use of SSZ-71 or SSZ-42 (disclosed in U.S. Pat. No. 5653956
issued Aug. 5 1997 to Zones) crystals as seed material can be advantageous
in decreasing the time necessary for complete crystallization to
occur. In addition, seeding can lead to an increased purity of the
product obtained by promoting the nucleation and/or formation of
SSZ-71 over any undesired phases. When used as seeds, as-synthesized
SSZ-71 or SSZ-42 crystals (containing the SDA) are added in an amount
between 0.1 and 10% of the weight of first tetravalent element oxide,
e.g. silica, used in the reaction mixture.
Once the molecular sieve crystals have formed, the solid product
is separated from the reaction mixture by standard mechanical separation
techniques such as filtration. The crystals are water-washed and
then dried, e.g., at 90.degree. C. to 150.degree. C. for from 8
to 24 hours, to obtain the as-synthesized SSZ-71 crystals. The drying
step can be performed at atmospheric pressure or under vacuum.
SSZ-71 as prepared has a mole ratio of an oxide selected from silicon
oxide, germanium oxide and mixtures thereof to an oxide selected
from zinc oxide, titanium oxide and mixtures thereof greater than
about 15. SSZ-71 further has a composition, as synthesized (i.e.,
prior to calcination of the SSZ-71) and in the anhydrous state,
in terms of mole ratios, shown in Table B below.
TABLE-US-00002 TABLE B As-Synthesized SSZ-71 YO.sub.2/WO.sub.d
>15 M.sub.2/n/YO.sub.2 0 0.03 Q/YO.sub.2 0.02 0.05
where Y, W, d, M, n and Q are as defined above.
SSZ-71 can be made with a mole ratio of YO.sub.2/WO.sub.d of .infin.,
i.e., there is essentially no WO.sub.d present in the SSZ-71. In
this case, the SSZ-71 would be an all-silica material or a germanosilicate.
If SSZ-71 is prepared as a zincosilicate, the zinc can be removed
and replaced with metal atoms by techniques known in the art. See,
for example, U.S. Pat. No. 6117411 issued Sep. 12 2000 to Takewaki
et al. Metals such as aluminum, gallium, iron, boron, titanium,
indium, vanadium and mixtures thereof may be added in this manner.
It is believed that SSZ-71 is comprised of a new framework structure
or topology which is characterized by its X-ray diffraction pattern.
SSZ-71 as-synthesized, has a structure whose X-ray powder diffraction
pattern exhibit the characteristic lines shown in Table I and Table
II and is thereby distinguished from other molecular sieves. The
XRD data shown in Table I and IA was obtained from a sample of SSZ-71
prepared in the presence of sodium hydroxide. The XRD data shown
in Table II and IIA was obtained from a sample of SSZ-71 prepared
in the presence of strontium hydroxide.
TABLE-US-00003 TABLE I As-Synthesized Zn-SSZ-71 Prepared with NaOH
2 Theta.sup.(a) d-spacing (Angstroms) Relative Intensity.sup.(b)
5.64 15.7 S 8.65 10.2 S 13.65 6.49 M 17.06 5.20 M 20.32 4.37 M 20.64
4.30 VS 23.12 3.85 M 24.08 3.70 VS 26.15 3.41 M 26.57 3.35 M .sup.(a).+-.
0.15 .sup.(b)The X-ray patterns provided are based on a relative
intensity scale in which the strongest line in the X-ray pattern
is assigned a value of 100: W(weak) is less than 20; M(medium) is
between 20 and 40; S(strong) is between 40 and 60; VS(very strong)
is greater than 60.
Table IA below shows the X-ray powder diffraction lines for as-synthesized
Zn-SSZ-71 prepared with NaOH including actual relative intensities.
TABLE-US-00004 TABLE IA 2 Theta.sup.(a) d-spacing (Angstroms) Relative
Intensity (%) 5.64 15.7 60 8.65 10.2 57 11.40 7.8 5 11.95 7.4 7
13.11 6.75 7 13.65 6.49 21 14.34 6.18 5 17.06 5.20 29 17.84 4.97
4 18.23 4.87 10 18.84 4.71 12 19.49 4.55 18 20.32 4.37 37 20.64
4.30 100 21.55 4.12 16 22.03 4.03 16 23.12 3.85 34 24.08 3.70 62
25.29 3.52 20 25.52 3.49 20 26.15 3.41 29 26.57 3.35 33 27.15 3.28
9 28.55 3.13 18 30.00 2.98 8 30.80 2.90 5 31.68 2.82 10 32.45 2.76
5 33.16 2.70 7 34.92 2.57 11 35.61 2.52 14 36.90 2.44 12 38.82 2.32
14 40.26 2.24 12 .sup.(a).+-. 0.15
TABLE-US-00005 TABLE II As-Synthesized Zn-SSZ-71 prepared with
Sr(OH).sub.2 2 Theta.sup.(a) d-spacing (Angstroms) Relative Intensity.sup.(b)
5.65 15.6 VS 8.69 10.2 VS 16.99 5.22 S 19.52 4.55 M 20.60 4.31 VS
23.13 3.85 M 24.01 3.71 S 24.23 3.67 M 26.14 3.41 M 26.52 3.36 M
.sup.(a).+-. 0.15 .sup.(b)The X-ray patterns provided are based
on a relative intensity scale in which the strongest line in the
X-ray pattern is assigned a value of 100: W(weak) is less than 20;
M(medium) is between 20 and 40; S(strong) is between 40 and 60;
VS(very strong) is greater than 60.
Table IIA below shows the X-ray powder diffraction lines for as-synthesized
SSZ-71 (Zn-SSZ-71 prepared with Sr(OH).sub.2) including actual relative
intensities.
TABLE-US-00006 TABLE IIA 2 Theta.sup.(a) d-spacing (Angstroms)
Relative Intensity (%) 5.65 15.6 84 8.69 10.2 67 11.36 7.8 5 11.94
7.4 5 13.17 6.7 7 13.68 6.5 20 14.34 6.18 6 15.31 5.79 2 16.99 5.22
42 18.24 4.86 8 18.79 4.72 17 19.52 4.55 26 20.34 4.37 23 20.60
4.31 100 21.59 4.12 13 22.06 4.03 16 23.13 3.85 37 24.01 3.71 41
24.23 3.67 25 25.25 3.53 20 25.52 3.49 23 26.14 3.41 36 26.52 3.36
30 27.10 3.29 12 28.52 3.13 22 29.85 2.99 6 30.24 2.96 2 30.84 2.90
3 31.64 2.83 11 32.44 2.76 5 33.11 2.71 5 34.86 2.57 6 35.63 2.52
14 36.10 2.49 6 .sup.(a).+-. 0.15
The X-ray powder diffraction patterns were determined by standard
techniques. The radiation was the K-alpha/doublet of copper. The
peak heights and the positions, as a function of 2.theta. where
.theta. is the Bragg angle, were read from the relative intensities
of the peaks, and d, the interplanar spacing in Angstroms corresponding
to the recorded lines, can be calculated.
The variation in the scattering angle (two theta) measurements,
due to instrument error and to differences between individual samples,
is estimated at .+-.0.15 degrees.
The X-ray diffraction pattern of Table I is representative of "as-synthesized"
or "as-made" SSZ-71 molecular sieves. Minor variations
in the diffraction pattern can result from variations in the silica-to-zinc
or silica-to-titanium mole ratio of the particular sample due to
changes in lattice constants. In addition, sufficiently small crystals
will affect the shape and intensity of peaks, leading to significant
peak broadening.
The molecular sieve produced by exchanging the metal or other cations
present in the molecular sieve with various other cations (such
as H.sup.+ or NH.sub.4.sup.+) yields essentially the same diffraction
pattern, although again, there may be minor shifts in the interplanar
spacing and variations in the relative intensities of the peaks.
Notwithstanding these minor perturbations, the basic crystal lattice
remains unchanged by these treatments.
SSZ-71 can be used as-synthesized, but preferably will be thermally
treated (calcined). Usually, it is desirable to remove the alkali
metal cation by ion exchange and replace it with hydrogen, ammonium,
or any desired metal ion. The molecular sieve can also be steamed;
steaming helps stabilize the molecular sieve to attack from acids.
The molecular sieve can be used in intimate combination with hydrogenating
components, such as tungsten, vanadium, molybdenum, rhenium, nickel,
cobalt, chromium, manganese, or a noble metal, such as palladium
or platinum, for those applications in which a hydrogenation-dehydrogenation
function is desired.
Metals may also be introduced into the molecular sieve by replacing
some of the cations in the molecular sieve with metal cations via
standard ion exchange techniques (see, for example, U.S. Pat. No.
3140249 issued Jul. 7 1964 to Plank et al.; U.S. Pat. No. 3140251
issued Jul. 7 1964 to Plank et al.; and U.S. Pat. No. 3140253
issued Jul. 7 1964 to Plank et al.). Typical replacing cations
can include metal cations, e.g., rare earth, Group IA, Group IIA
and Group VIII metals, as well as their mixtures. Of the replacing
metallic cations, cations of metals such as rare earth, Mn, Ca,
Mg, Zn, Cd, Pt, Pd, Ni, Co, Ti, Al, Sn, and Fe are particularly
preferred.
The hydrogen, ammonium, and metal components can be ion-exchanged
into the SSZ-71. The SSZ-71 can also be impregnated with the metals,
or the metals can be physically and intimately admixed with the
SSZ-71 using standard methods known to the art.
Typical ion-exchange techniques involve contacting the synthetic
molecular sieve with a solution containing a salt of the desired
replacing cation or cations. Although a wide variety of salts can
be employed, chlorides and other halides, acetates, nitrates, and
sulfates are particularly preferred. The molecular sieve is usually
calcined prior to the ion-exchange procedure to remove the organic
matter present in the channels and on the surface, since this results
in a more effective ion exchange. Representative ion exchange techniques
are disclosed in a wide variety of patents including U.S. Pat. No.
3140249 issued on Jul. 7 1964 to Plank et al.; U.S. Pat. No.
3140251 issued on Jul. 7 1964 to Plank et al.; and U.S. Pat.
No. 3140253 issued on Jul. 7 1964 to Plank et al.
Following contact with the salt solution of the desired replacing
cation, the molecular sieve is typically washed with water and dried
at temperatures ranging from 65.degree. C. to about 200.degree.
C. After washing, the molecular sieve can be calcined in air or
inert gas at temperatures ranging from about 200.degree. C. to about
800.degree. C. for periods of time ranging from 1 to 48 hours, or
more, to produce a catalytically active product especially useful
in hydrocarbon conversion processes.
Regardless of the cations present in the synthesized form of SSZ-71
the spatial arrangement of the atoms which form the basic crystal
lattice of the molecular sieve remains essentially unchanged.
SSZ-71 can be formed into a wide variety of physical shapes. Generally
speaking, the molecular sieve can be in the form of a powder, a
granule, or a molded product, such as extrudate having a particle
size sufficient to pass through a 2-mesh (Tyler) screen and be retained
on a 400-mesh (Tyler) screen. In cases where the catalyst is molded,
such as by extrusion with an organic binder, the SSZ-71 can be extruded
before drying, or, dried or partially dried and then extruded.
SSZ-71 can be composited with other materials resistant to the
temperatures and other conditions employed in organic conversion
processes. Such matrix materials include active and inactive materials
and synthetic or naturally occurring zeolites as well as inorganic
materials such as clays, silica and metal oxides. Examples of such
materials and the manner in which they can be used are disclosed
in U.S. Pat. No. 4910006 issued May 20 1990 to Zones et al.,
and U.S. Pat. No. 5316753 issued May 31 1994 to Nakagawa, both
of which are incorporated by reference herein in their entirety.
The molecular sieve of the present invention can be used in a catalyst
for acylating an aromatic substrate ArH.sub.n, where n is at least
1 by reacting the aromatic substrate with an acylating agent in
the presence of the catalyst. The product of the acylation reaction
is ArH.sub.n-1COR where R is an organic radical.
Examples of the aromatic substrate include, but are not limited
to, benzene, toluene, anisole and 2-naphthol. Examples of the acylating
agent included, but are not limited to, carboxylic acid derivatives,
carboxylic acids, acid anhydrides, esters, and acyl halides.
Reaction conditions are known in the art (see, for example, U.S.
Pat. No. 6630606 issued Oct. 7 2003 to Poliakoff et al., U.S.
Pat. No. 6459000 issued Oct. 1 2002 to Choudhary et al., and
U.S. Pat. No. 6548722 issued Apr. 15 2003 to Choudhary et al.,
all of which are incorporated herein by reference in their entirety).
Typically, the acylation reaction is conducted with a weight ratio
of the catalyst to the acylating agent of about 0.03 to about 0.5
a mole ratio of aromatic substrate to acylating agent of about 1.0
to about 20 a reaction temperature in the range of about 20.degree.
C. to about 200.degree. C., a reaction pressure in the range of
about 1 atm to about 5 atm, and a reaction time of about 0.05 hours
to about 20 hours. |