Molecular sieve abstract
The present invention relates to new crystalline molecular sieve
SSZ-70 prepared using a N,N'-diisopropyl imidazolium cation as a
structure-directing agent, methods for synthesizing SSZ-70 and processes
employing SSZ-70 in a catalyst.
Molecular sieve claims
1. A process for oxidation of hydrocarbons comprising contacting
said hydrocarbon with an oxidizing agent in the presence of a catalytically
effective amount of a crystalline, titanium-containing molecular
sieve for a time and at a temperature effective to oxidize said
hydrocarbon, wherein the crystalline titanium-containing molecular
sieve is a molecular sieve having a mole ratio greater than about
15 of (1) silicon oxide to (2) titanium oxide, and having, after
calcination, the X-ray diffraction lines of Table II.
2. A process for epoxidation of an olefin comprising contacting
said olefin with hydrogen peroxide in the presence of a catalytically
effective amount of a crystalline, titanium-containing molecular
sieve for a time and at a temperature effective to epoxidize said
olefin, wherein the crystalline titanium-containing molecular sieve
is a molecular sieve having a mole ratio greater than about 15 of
(1) silicon oxide to (2) titanium oxide, and having, after calcination,
the X-ray diffraction lines of Table II.
3. A process for oxidizing cyclohexane comprising contacting said
cyclohexane with hydrogen peroxide in the presence of a catalytically
effective amount of a crystalline, titanium-containing molecular
sieve for a time and at a temperature effective to oxidize said
cyclohexane, wherein the crystalline titanium-containing molecular
sieve is a molecular sieve having a mole ratio greater than about
15 of (1) silicon oxide to (2) titanium oxide, and having, after
calcination, the X-ray diffraction lines of Table II.
4. A catalytic oxidation process comprising contacting under oxidation
conditions (1) a reactant which is catalytically oxidizable in the
presence of hydrogen peroxide, (2) aqueous hydrogen peroxide and
(3) a catalytically effective amount of an oxidation catalyst comprising
a molecular sieve having a mole ratio greater than about 15 of (1)
silicon oxide to (2) titanium oxide, and having, after calcination,
the X-ray diffraction lines of Table II.
5. The process of claim 4 wherein the elemental mole ratio of titanium
to silicon is about 0.005 to about 0.2.
6. The process of claim 4 wherein the elemental mole ratio of titanium
to silicon is about 0.01 to about 0.05.
7. The process of claim 4 wherein the oxidizable reactant is a
hydrocarbon.
8. A process for the epoxidation of an olefin comprising contacting
said olefin with hydrogen peroxide in the presence of a catalytically
effective amount of a catalyst comprising a molecular sieve having
a mole ratio greater than about 15 of (1) silicon oxide to (2) titanium
oxide, and having, after calcination, the X-ray diffraction lines
of Table II.
9. The process of claim 8 wherein the elemental mole ratio of titanium
to silicon is about 0.005 to about 0.2.
10. The process of claim 8 wherein the elemental mole ratio of
titanium to silicon is about 0.01 to about 0.05.
Molecular sieve description
[0001] This application claims benefit under 35 USC 119 of Provisional
Application 60/639212 filed Dec. 23 2004.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to new crystalline molecular
sieve SSZ-70 a method for preparing SSZ-70 using a N,N'-diisopropyl
imidazolium cation as a structure directing agent and the use of
SSZ-70 in catalysts for, e.g., hydrocarbon conversion reactions.
[0004] 2. State of the Art
[0005] 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.
[0006] 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
[0007] The present invention is directed to a family of crystalline
molecular sieves with unique properties, referred to herein as "molecular
sieve SSZ-70" or simply "SSZ-70". Preferably, SSZ-70
is obtained in its silicate, aluminosilicate, titanosilicate, vanadosilicate
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 "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.
[0008] In accordance with the present invention, there is provided
a process for oxidation of hydrocarbons comprising contacting said
hydrocarbon with an oxidizing agent in the presence of a catalytically
effective amount of a crystalline, titanium-containing molecular
sieve for a time and at a temperature effective to oxidize said
hydrocarbon, wherein the crystalline titanium-containing molecular
sieve is a molecular sieve having a mole ratio greater than about
15 of (1) silicon oxide to (2) titanium oxide, and having, after
calcination, the X-ray diffraction lines of Table II.
[0009] There is further provided in accordance with this invention
a process for epoxidation of an olefin comprising contacting said
olefin with hydrogen peroxide in the presence of a catalytically
effective amount of a crystalline, titanium-containing molecular
sieve for a time and at a temperature effective to epoxidize said
olefin, wherein the crystalline titanium-containing molecular sieve
is a molecular sieve having a mole ratio greater than about 15 of
(1) silicon oxide to (2) titanium oxide, and having, after calcination,
the X-ray diffraction lines of Table II.
[0010] Further provided in accordance with the present invention
is a process for oxidizing cyclohexane comprising contacting said
cyclohexane with hydrogen peroxide in the presence of a catalytically
effective amount of a crystalline, titanium-containing molecular
sieve for a time and at a temperature effective to oxidize said
cyclohexane, wherein the crystalline titanium-containing molecular
sieve is a molecular sieve having a mole ratio greater than about
15 of (1) silicon oxide to (2) titanium oxide, and having, after
calcination, the X-ray diffraction lines of Table II.
[0011] The present invention also provides a catalytic oxidation
process comprising contacting under oxidation conditions (1) a reactant
which is catalytically oxidizable in the presence of hydrogen peroxide,
(2) aqueous hydrogen peroxide and (3) a catalytically effective
amount of an oxidation catalyst comprising a molecular sieve having
a mole ratio greater than about 15 of (1) silicon oxide to (2) titanium
oxide, and having, after calcination, the X-ray diffraction lines
of Table II.
[0012] The present invention also provides a process for the epoxidation
of an olefin comprising contacting said olefin with hydrogen peroxide
in the presence of a catalytically effective amount of a catalyst
comprising a molecular sieve having a mole ratio greater than about
15 of (1) silicon oxide to (2) titanium oxide, and having, after
calcination, the X-ray diffraction lines of Table II.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is an X-ray diffraction pattern of SSZ-70 after it
has been calcined.
[0014] FIG. 2 is an X-ray diffraction pattern of SSZ-70 in the
as-synthesized form, i.e., prior to calcination with the SDA still
in the pores of the SSZ-70.
DETAILED DESCRIPTION OF THE INVENTION
[0015] The present invention comprises a family of crystalline
molecular sieves designated herein "molecular sieve SSZ-70"
or simply "SSZ-70". In preparing SSZ-70 a N,N'-diisopropyl
imidazolium cation (referred to herein as "DIPI") is used
as a structure directing agent ("SDA"), also known as
a crystallization template. The SDA useful for making SSZ-70 has
the following structure:
[0016] 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.
[0017] SSZ-70 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/B.sub.2O.sub.3 5-60 10-60 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 30-80 35-45 F/YO.sub.2 0-0.50
0
where Y is silicon; M is an alkali metal cation, alkaline earth
metal cation or mixtures thereof; n is the valence of M (i.e., 1
or 2); F is fluorine and Q is a N,N'-diisopropyl imidazolium cation.
[0018] In practice, SSZ-70 is prepared by a process comprising:
[0019] (a) preparing an aqueous solution containing sources of at
least two oxides capable of forming a crystalline molecular sieve
and a DIPI cation having an anionic counterion which is not detrimental
to the formation of SSZ-70; [0020] (b) maintaining the aqueous solution
under conditions sufficient to form crystals of SSZ-70; and [0021]
(c) recovering the crystals of SSZ-70.
[0022] Accordingly, SSZ-70 may comprise the crystalline material
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. Typical
sources of silicon oxide include silicates, silica hydrogel, silicic
acid, fumed silica, colloidal silica, tetra-alkyl orthosilicates,
and silica hydroxides. Boron can be added in forms corresponding
to its silicon counterpart, such as boric acid.
[0023] A source zeolite reagent may provide a source of boron.
In most cases, the source zeolite also provides a source of silica.
The source zeolite in its deboronated form 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
for the present process is more completely 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.
[0024] Typically, an alkali metal hydroxide and/or an alkaline
earth metal hydroxide, such as the hydroxide of sodium, potassium,
lithium, cesium, rubidium, calcium, 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 crystalline
oxide material, in order to balance valence electron charges therein.
[0025] The reaction may also be carried out using HF to counterbalance
the OH-contribution from the SDA, and run the synthesis in the absence
of alkali cations. Running in the absence of alkali cations has
the advantage of being able to prepare a catalyst from the synthesis
product, by using calcination alone, i.e., no ion-exchange step
(to remove alkali or alkaline earth cations) is necessary. In using
HF, the reaction operates best when both the SDA and HF have mole
ratios of 0.50 relative to YO.sub.2 (e.g., silica).
[0026] The reaction mixture is maintained at an elevated temperature
until the crystals of the SSZ-70 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.
[0027] Preferably, the molecular sieve is prepared using mild stirring
or agitation.
[0028] During the hydrothermal crystallization step, the SSZ-70
crystals can be allowed to nucleate spontaneously from the reaction
mixture. The use of SSZ-70 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-70 over any undesired phases. When used as seeds, SSZ-70 crystals
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.
[0029] 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-70 crystals. The
drying step can be performed at atmospheric pressure or under vacuum.
[0030] SSZ-70 as prepared has a mole ratio of (1) silicon oxide
to (2) boron oxide greater than about 15; and has, after calcination,
the X-ray diffraction lines of Table II below. SSZ-70 further has
a composition, as synthesized (i.e., prior to removal of the SDA
from the SSZ-70) and in the anhydrous state, in terms of mole ratios,
shown in Table B below. TABLE-US-00002 TABLE B As-Synthesized SSZ-70
YO.sub.2/B.sub.2O.sub.3 20-60 M.sub.2/n/YO.sub.2 0-0.03 Q/YO.sub.2
0.02-0.05 F/YO.sub.2 0-0.10
where Y, M, n, F is fluorine and Q are as defined above.
[0031] SSZ-70 can be an essentially all-silica material. As used
herein, "essentially all-silica" means that the molecular
sieve is comprised of only silicon oxide or is comprised of silicon
oxide and only trace amounts of other oxides, such as aluminum oxide,
which may be introduced as impurities in the source of silicon oxide.
Thus, in a typical case where oxides of silicon and boron are used,
SSZ-70 can be made essentially boron free, i.e., having a silica
to boron oxide mole ratio of .infin.. SSZ-70 is made as a borosilicate
and then the boron can then be removed, if desired, by treating
the borosilicate SSZ-70 with acetic acid at elevated temperature
(as described in Jones et al., Chem. Mater., 2001 13 1041-1050)
to produce an essentially all-silica version of SSZ-70.
[0032] If desired, SSZ-70 can be made as a borosilicate and then
the boron can be removed as described above and replaced with metal
atoms by techniques known in the art. Aluminum, gallium, iron, titanium,
vanadium and mixtures thereof can be added in this manner.
[0033] It is believed that SSZ-70 is comprised of a new framework
structure or topology which is characterized by its X-ray diffraction
pattern. SSZ-70 as-synthesized, has a crystalline structure whose
X-ray powder diffraction pattern exhibit the characteristic lines
shown in Table I and is thereby distinguished from other molecular
sieves. TABLE-US-00003 TABLE I As-Synthesized SSZ-70 d-spacing Relative
2 Theta.sup.(a) (Angstroms) Intensity (%).sup.(b) 3.32 26.6 VS 6.70
13.2 VS 7.26 12.2 S 8.78 10.1 S 13.34 6.64 M 20.02 4.44 S 22.54
3.94 M 22.88 3.89 M 26.36 3.38 S-VS 26.88 3.32 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.
[0034] Table IA below shows the X-ray powder diffraction lines
for as-synthesized SSZ-70 including actual relative intensities.
TABLE-US-00004 TABLE IA 2 Theta.sup.(a) d-spacing (Angstroms) Relative
Intensity (%) 3.32 26.6 84 6.70 13.2 100 7.26 12.2 45 8.78 10.1
44 13.34 6.64 26 20.02 4.44 46 22.54 3.94 33 22.88 3.89 36 26.36
3.38 61 26.88 3.32 31 .sup.(a).+-.0.15
[0035] After calcination, the SSZ-70 molecular sieves have a crystalline
structure whose X-ray powder diffraction pattern include the characteristic
lines shown in Table II: TABLE-US-00005 TABLE II Calcined SSZ-70
2 Theta.sup.(a) d-spacing (Angstroms) Relative Intensity (%) 7.31
12.1 VS 7.75 11.4 VS 9.25 9.6 VS 14.56 6.08 VS 15.61 5.68 S 19.60
4.53 S 21.81 4.07 M 22.24 4.00 M-S 26.30 3.39 VS 26.81 3.33 VS .sup.(a).+-.0.15
[0036] Table IIA below shows the X-ray powder diffraction lines
for calcined SSZ-70 including actual relative intensities. TABLE-US-00006
TABLE IIA 2 Theta.sup.(a) d-spacing (Angstroms) Relative Intensity
(%) 7.31 12.1 67 7.75 11.4 93 9.25 9.6 79 14.56 6.08 68 15.61 5.68
49 19.60 4.53 58 21.81 4.07 38 22.24 4.00 41 26.30 3.39 99 26.81
3.33 80 .sup.(a).+-.0.15
[0037] 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.
[0038] 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.
[0039] The X-ray diffraction pattern of Table I is representative
of "as-synthesized" or "as-made" SSZ-70 molecular
sieves. Minor variations in the diffraction pattern can result from
variations in the silica-to-boron 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.
[0040] Representative peaks from the X-ray diffraction pattern
of calcined SSZ-70 are shown in Table II. Calcination can also result
in changes in the intensities of the peaks as compared to patterns
of the "as-made" material, as well as minor shifts in
the diffraction pattern. 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.
[0041] Crystalline SSZ-70 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 be leached with chelating agents, e.g., EDTA or dilute acid
solutions, to increase the silica to alumina mole ratio. The molecular
sieve can also be steamed; steaming helps stabilize the crystalline
lattice to attack from acids.
[0042] 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.
[0043] 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.
[0044] The hydrogen, ammonium, and metal components can be ion-exchanged
into the SSZ-70. The SSZ-70 can also be impregnated with the metals,
or the metals can be physically and intimately admixed with the
SSZ-70 using standard methods known to the art.
[0045] 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.
[0046] 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.
[0047] Regardless of the cations present in the synthesized form
of SSZ-70 the spatial arrangement of the atoms which form the basic
crystal lattice of the molecular sieve remains essentially unchanged.
[0048] SSZ-70 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-70 can be extruded before drying, or, dried or partially
dried and then extruded.
[0049] SSZ-70 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.
[0050] The partial oxidation of low value hydrocarbons such as
alkanes and alkenes into high value products such as alcohols and
epoxides is of great commercial interest. These oxidation products
are not only valuable as is, but also as intermediates for specialty
chemicals including pharmaceuticals and pesticides.
[0051] U.S. Pat. No. 4410501 issued Oct. 18 1983 to Esposito
et al., discloses a titanium-containing analogue of the all-silica
ZSM-5 molecular sieve. This material (known as "TS-1")
has been found to be useful in catalyzing a wide range of partial
oxidation chemistries, for example the production of catechol and
hydroquinone from phenol and hydrogen peroxide (H.sub.2O.sub.2)
and the manufacture of propylene oxide and cyclohexanone oxime from
propylene and cyclohexanone, respectively. In addition, TS-1 can
be used to catalyze the reaction of alkanes and aqueous H.sub.2O.sub.2
to form alcohols and ketones. (See Huybrechts, D. R. C. et al.,
Nature 1990 345 240-242 and Tatsumi, T. et al., J.C.S. Chem. Commun.
1990 476-477.)
[0052] TS-1 has many salient features, other than its catalytic
abilities, which make it attractive as a commercial catalyst. Most
importantly, it is a solid. This allows for easy separation from
the reactants and products (typically liquids) by simple, inexpensive
filtration. Moreover, this solid has high thermal stability and
a very long lifetime. Calcination in air at moderate temperatures
(550.degree. C.) restores the material to its original catalytic
ability. TS-1 performs best at mild temperatures (<100.degree.
C.) and pressures (1 atm). The oxidant used for reactions catalyzed
by TS-1 is aqueous H.sub.2O.sub.2 which is important because aqueous
H.sub.2O.sub.2 is relatively inexpensive and its by-product is water.
Hence, the choice of oxidant is favorable from both a commercial
and environmental point of view.
[0053] While a catalyst system based on TS-1 has many useful features,
it has one serious drawback. The zeolite structure of TS-1 includes
a regular system of pores which are formed by nearly circular rings
of ten silicon atoms (called 10-membered rings, or simply "10
rings") creating pore diameters of approximately 5.5 .ANG..
This small size results in the exclusion of molecules larger than
5.5 .ANG.. Because the catalytically active sites are located within
the pores of the zeolite, any exclusion of molecules from the pores
results in poor catalytic activity.
[0054] SSZ-70 containing titanium oxide (Ti-SSZ-70) is useful as
a catalyst in oxidation reactions, particularly in the oxidation
of hydrocarbons. Examples of such reactions include, but are not
limited to, the epoxidation of olefins, the oxidation of alkanes,
and the oxidation of sulfur-containing, nitrogen-containing or phosphorus-containing
compounds.
[0055] The amount of Ti-SSZ-70 catalyst employed is not critical,
but should be sufficient so as to substantially accomplish the desired
oxidation reaction in a practicably short period of time (i.e.,
a catalytically effective amount). The optimum quantity of catalyst
will depend upon a number of factors including reaction temperature,
the reactivity and concentration of the substrate, hydrogen peroxide
concentration, type and concentration of organic solvent, as well
as the activity of the catalyst. Typically, however, the amount
of catalyst will be from about 0.001 to 10 grams per mole of substrate.
[0056] Typically, the Ti-SSZ-70 is thermally treated (calcined)
prior to use as a catalyst.
[0057] The oxidizing agent employed in the oxidation processes
of this invention is a hydrogen peroxide source such as hydrogen
peroxide (H.sub.2O.sub.2) or a hydrogen peroxide precursor (i.e.,
a compound which under the oxidation reaction conditions is capable
of generating or liberating hydrogen peroxide).
[0058] The amount of hydrogen peroxide relative to the amount of
substrate is not critical, but must be sufficient to cause oxidation
of at least some of the substrate. Typically, the molar ratio of
hydrogen peroxide to substrate is from about 100:1 to about 1:100
preferably 10:1 to about 1:10. When the substrate is an olefin containing
more than one carbon-carbon double bond, additional hydrogen peroxide
may be required. Theoretically, one equivalent of hydrogen peroxide
is required to oxidize one equivalent of a mono-unsaturated substrate,
but it may be desirable to employ an excess of one reactant to optimize
selectivity to the epoxide. In particular, the use of a moderate
to large excess (e.g., 50 to 200%) of olefin relative to hydrogen
peroxide may be advantageous for certain substrates.
[0059] If desired, a solvent may additionally be present during
the oxidation reaction in order to dissolve the reactants other
than the Ti-SSZ-70 to provide better temperature control, or to
favorably influence the oxidation rates and selectivities. The solvent,
if present, may comprise from 1 to 99 weight percent of the total
oxidation reaction mixture and is preferably selected such that
it is a liquid at the oxidation reaction temperature. Organic compounds
having boiling points at atmospheric pressure of from about 50.degree.
C. to about 150.degree. C. are generally preferred for use. Excess
hydrocarbon may serve as a solvent or diluent. Illustrative examples
of other suitable solvents include, but are not limited to, ketones
(e.g., acetone, methyl ethyl ketone, acetophenone), ethers (e.g.,
tetrahydrofuran, butyl ether), nitrites (e.g., acetonitrile), aliphatic
and aromatic hydrocarbons, halogenated hydrocarbons, and alcohols
(e.g., methanol, ethanol, isopropyl alcohol, t-butyl alcohol, alpha-methyl
benzyl alcohol, cyclohexanol). More than one type of solvent may
be utilized. Water may also be employed as a solvent or diluent.
[0060] The reaction temperature is not critical, but should be
sufficient to accomplish substantial conversion of the substrate
within a reasonably short period of time. It is generally advantageous
to carry out the reaction to achieve as high a hydrogen peroxide
conversion as possible, preferably at least about 50%, more preferably
at least about 90%, most preferably at least about 95%, consistent
with reasonable selectivities. The optimum reaction temperature
will be influenced by catalyst activity, substrate reactivity, reactant
concentrations, and type of solvent employed, among other factors,
but typically will be in a range of from about 0.degree. C. to about
150.degree. C. (more preferably from about 25.degree. C. to about
120.degree. C.). Reaction or residence times from about one minute
to about 48 hours (more desirably from about ten minutes to about
eight hours) will typically be appropriate, depending upon the above-identified
variables. Although subatmospheric pressures can be employed, the
reaction is preferably performed at atmospheric or at elevated pressure
(typically, between one and 100 atmospheres), especially when the
boiling point of the substrate is below the oxidation reaction temperature.
Generally, it is desirable to pressurize the reaction vessel sufficiently
to maintain the reaction components as a liquid phase mixture. Most
(over 50%) of the substrate should preferably be present in the
liquid phase.
[0061] The oxidation process of this invention may be carried out
in a batch, continuous, or semi-continuous manner using any appropriate
type of reaction vessel or apparatus such as a fixed bed, transport
bed, fluidized bed, stirred slurry, or CSTR reactor. The reactants
may be combined all at once or sequentially. For example, the hydrogen
peroxide or hydrogen peroxide precursor may be added incrementally
to the reaction zone. The hydrogen peroxide could also be generated
in situ within the same reactor zone where oxidation is taking place.
[0062] Once the oxidation has been carried out to the desired degree
of conversion, the oxidized product may be separated and recovered
from the reaction mixture using any appropriate technique such as
fractional distillation, extractive distillation, liquid-liquid
extraction, crystallization, or the like.
Olefin Epoxidation
[0063] One of the oxidation reactions for which Ti-SSZ-70 is useful
as a catalyst is the epoxidation of olefins. The olefin substrate
epoxidized in the process of this invention may be any organic compound
having at least one ethylenically unsaturated functional group (i.e.,
a carbon-carbon double bond) and may be a cyclic, branched or straight-chain
olefin. The olefin may contain aryl groups (e.g., phenyl, naphthyl).
Preferably, the olefin is aliphatic in character and contains from
2 to about 20 carbon atoms. The use of light (low-boiling) C.sub.2
to C.sub.10 mono-olefins is especially advantageous.
[0064] More than one carbon-carbon double bond may be present in
the olefin, i.e., dienes, trienes and other polyunsaturated substrates
may be used. The double bond may be in a terminal or internal position
in the olefin or may alternatively form part of a cyclic structure
(as in cyclooctene, for example).
[0065] Other examples of suitable substrates include unsaturated
fatty acids or fatty acid derivatives such as esters.
[0066] The olefin may contain substituents other than hydrocarbon
substituents such as halide, carboxylic acid, ether, hydroxy, thiol,
nitro, cyano, ketone, acyl, ester, anhydride, amino, and the like.
[0067] Exemplary olefins suitable for use in the process of this
invention include ethylene, propylene, the butenes (i.e., 12-butene,
23-butene, isobutylene), butadiene, the pentenes, isoprene, 1-hexene,
3-hexene, 1-heptene, 1-octene, diisobutylene, 1-nonene, 1-tetradecene,
pentamyrcene, camphene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene,
1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene,
1-eicosene, the trimers and tetramers of propylene, cyclopentene,
cyclohexene, cycloheptene, cyclooctene, cyclooctadiene, dicyclopentadiene,
methylenecyclopropane, methylenecyclopentane, methylenecyclohexane,
vinyl cyclohexane, vinyl cyclohexene, methallyl ketone, allyl chloride,
the dichlorobutenes, allyl alcohol, allyl carbonate, allyl acetate,
alkyl acrylates and methacrylates, diallyl maleate, diallyl phthalate,
and unsaturated fatty acids, such as oleic acid, linolenic acid,
linoleic acid, erucic acid, palmitoleic acid, and ricinoleic acid
and their esters (including mono-, di-, and triglyceride esters)
and the like.
[0068] Olefins which are especially useful for epoxidation are
the C.sub.2-C.sub.20 olefins having the general structure R.sup.3R.sup.4C.dbd.CR.sup.5R.sup.6
wherein R.sup.3 R.sup.4 R.sup.5 and R.sup.6 are the same or different
and are selected from the group consisting of hydrogen and C.sub.1-C.sub.18
alkyl.
[0069] Mixtures of olefins may be epoxidized and the resulting
mixtures of epoxides either employed in the mixed form or separated
into the different component epoxides.
[0070] The present invention further provides a process for oxidation
of hydrocarbons comprising contacting said hydrocarbon with hydrogen
peroxide in the presence of a catalytically effective amount of
Ti-SSZ-70 for a time and at a temperature effective to oxidize said
hydrocarbon.
EXAMPLES
[0071] The following examples demonstrate but do not limit the
present invention.
Examples 1-6
Synthesis of Borosilicate SSZ-70 (B-SSZ-70)
[0072] B-SSZ-70 is synthesized by preparing the gel compositions,
i.e., reaction mixtures, having the compositions, in terms of mole
ratios, shown in the table below. The resulting gel is placed in
a Parr bomb reactor and heated in an oven at the temperature (.degree.
C.) indicated in the table while rotating at 43 rpm. Amounts in
the table are in millimoles. Products are analyzed by X-ray diffraction
(XRD) and found to be B-SSZ-70 or a mixture of B-SSZ-70 and amorphous
material. TABLE-US-00007 Ex. No. SiO.sub.2 DIPI H.sub.2O/SiO.sub.2
HF H.sub.3BO.sub.3 Temp., .degree. C. Seeds Days Prod. 1 18 9 15
9 1.0 150 No 95 AM/ B- SSZ- 70 2 18 9 15 9 1.0 150 Yes 98 AM/ B-
SSZ- 70 3 18 9 15 9 1.0 170 No 52 B- SSZ- 70 4 18 9 15 9 1.0 150
Yes 80 B- SSZ- 70 5 18 9 15 9 3.3 170 No 52 B- SSZ- 70 6 18 9 15
9 5.0 170 No 61 B- SSZ-70 AM = amorphous material
[0073] The X-ray diffraction lines for as-synthesized SSZ-70 are
shown in the table below. TABLE-US-00008 As-Synthesized SSZ-70 XRD
2 Theta.sup.(a) d-spacing (Angstroms) Relative Intensity (%) 3.32
26.6 84 6.70 13.2 100 7.26 12.2 45 8.78 10.1 44 10.04 8.81 20 10.88
8.13 17 13.00 6.81 16 13.34 6.64 26 14.60 6.07 23 15.36 5.77 14
16.66 5.32 10 18.54 4.79 6 19.30 4.60 14 20.02 4.44 46 21.86 4.07
25 22.54 3.94 33 22.88 3.89 36 24.38 3.65 13 25.28 3.52 25 26.36
3.38 61 26.88 3.32 31 29.56 3.02 6 32.00 2.80 8 33.61 2.67 4 36.94
2.43 5 38.40 2.34 7 .sup.(a).+-.0.15
Example 7
[0074] A run is set up as in the table above but the mole ratios
are as follows: SiO.sub.2=16 mmoles, DIPI=5 mmoles, H.sub.3BO.sub.3=4
mmoles and water=240 mmoles. No HF component is used. The reaction
is run for only seven days at 43 RPM at 170.degree. C. The product
is SSZ-70.
Example 8
Calcination of SSZ-70
[0075] SSZ-70 is calcined to remove the structure directing agent
(SDA) as described below. A thin bed of SSZ-70 in a calcination
dish is heated in a muffle furnace from room temperature to 120.degree.
C. at a rate of 1.degree. C./minute and held for 2 hours. Then,
the temperature is ramped up to 540.degree. C. at a rate of 1.degree.
C./minute and held for 5 hours. The temperature is ramped up again
at 1.degree. C./minute to 595.degree. C. and held there for 5 hours.
A 50/50 mixture of air and nitrogen passes through the muffle furnace
at a rate of 20 standard cubic feet (0.57 standard cubic meters)
per minute during the calcination process. The XRD lines for calcined
SSZ-70 are shown in the table below. TABLE-US-00009 2 Theta.sup.(a)
d-spacing (Angstroms) Relative Intensity (%) 3.93 22.5 22 7.31 12.1
67 7.75 11.4 93 9.25 9.6 79 14.56 6.08 68 15.61 5.68 49 17.34 5.11
15 19.60 4.53 58 21.81 4.07 38 22.24 4.00 41 23.11 3.85 77 25.30
3.52 23 26.30 3.39 99 26.81 3.33 80 .sup.(a).+-.0.15
Example 9
Replacement of Boron with Aluminum
[0076] Calcined SSZ-70 (about 5 grams) is combined with 500 grams
of 1 M aqueous Al(NO.sub.3).sub.3 solution and treated under reflux
for 100 hours. The resulting aluminum-containing SSZ-70 product
is then washed with 100 ml 0.01N HCl and then with one liter of
water, filtered and air dried at room temperature in a vacuum filter.
Example 10
Constraint Index
[0077] The hydrogen form of calcined SSZ-70 is pelletized at 3
KPSI, crushed and granulated to 20-40 mesh. A 0.6 gram sample of
the granulated material is calcined in air at 540.degree. C. for
4 hours and cooled in a desiccator to ensure dryness. Then, 0.5
gram is packed into a 3/8 inch stainless steel tube with alundum
on both sides of the molecular sieve bed. A Lindburg furnace is
used to heat the reactor tube. Helium is introduced into the reactor
tube at 10 cc/min. and at atmospheric pressure. The reactor is heated
to about 427.degree. C. (800.degree. F.), and a 50/50 feed of n-hexane
and 3-methylpentane is introduced into the reactor at a rate of
8 .mu.l/min. The feed is delivered by a Brownlee pump. Direct sampling
into a GC begins after 10 minutes of feed introduction. The Constraint
Index (CI) value is calculated from the GC data using methods known
in the art. The results are shown in the table below. TABLE-US-00010
Time, Min. 10 40 70 100 Feed Conv. % 6.4 6.5 6.5 6.4 CI (excl. 2-
0.6 0.59 0.56 0.56 MP) CI (incl. 2-MP) 0.78 0.79 0.75 0.76 2-MP
= 2-methylpentane
Example 11
Hydrocracking of n-Hexadecane
[0078] A 1 gm sample of calcined SSZ-70 is suspended in 10 gm de-ionized
water. To this suspension, a solution of Pt(NH.sub.3).sub.4.(NO.sub.3).sub.2
at a concentration which would provide 0.5 wt. % Pt with respect
to the dry weight of the molecular sieve sample is added. The pH
of the solution is adjusted to pH of .about.9 by a drop-wise addition
of dilute ammonium hydroxide solution. The mixture is then allowed
to stand at 25.degree. C. for 48 hours. The mixture is then filtered
through a glass frit, washed with de-ionized water, and air-dried.
The collected Pt-SSZ-70 sample is slowly calcined up to 288.degree.
C. in air and held there for three hours.
[0079] The calcined Pt/SSZ-70 catalyst is pelletized in a Carver
Press and granulated to yield particles with a 20/40 mesh size.
Sized catalyst (0.5 g) is packed into a 1/4 inch OD tubing reactor
in a micro unit for n-hexadecane hydroconversion. The table below
gives the run conditions and the products data for the hydrocracking
test on n-hexadecane.
[0080] The results shown in the table below show that SSZ-70 is
effective as a hydrocracking catalyst. The data show that the catalyst
has a very high selectivity for hydrocracking to linear paraffins,
rather than isomerization selectivity. Also, a high ratio of liquid/gas
(C.sub.5+/C.sub.4-) is achieved. TABLE-US-00011 Temperature 660.degree.
F. (349.degree. C.) 690.degree. F. (366.degree. C.) Time-on-Stream
(hrs.) 40 hours 53 hours PSIG 2200 2200 Titrated? No No n-16 %
Conversion 52% 89% Isomerization Selectivity, % 5.1 2.2 C.sub.5+/C.sub.4-
11.5 7.0 C.sub.4-C.sub.13 i/n 0.02 0.03
Example 12
Micropore Volume
[0081] SSZ-70 has a micropore volume of 0.071 cc/gm based on argon
adsorption isotherm at 87.5.degree. K (-186.degree. C.) recorded
on ASAP 2010 equipment from Micromerities. The sample is first degassed
at 400.degree. C. for 16 hours prior to argon adsorption. The low-pressure
dose is 2.00 cm.sup.3/g (STP). A maximum of one hour equilibration
time per dose is used and the total run time is 37 hours. The argon
adsorption isotherm is analyzed using the density function theory
(DFT) formalism and parameters developed for activated carbon slits
by Olivier (Porous Mater. 1995 2 9) using the Saito Foley adaptation
of the Horvarth-Kawazoe formalism (Microporous Materials, 1995
3 531) and the conventional t-plot method (J. Catalysis, 1965
4 319) (micropore volume by the t-plot method is 0.074 cc/gm).
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