Molecular sieve abstract
A novel crystalline aluminophosphate and metalloaluminophosphate
of the molecular sieve type, denominated SSZ-51 is prepared by
hydrothermal synthesis from reactive sources of aluminum and phosphorus,
fluorine and an organic templating agent, 4-dimethylaminopyridine.
Molecular sieve claims
What is claimed is:
1. A molecular sieve whose chemical composition, expressed in terms
of mole ratios of oxides after calcination, is: Al.sub.2O.sub.3:1.0.+-.0.2P.-
sub.2O.sub.5:xSiO.sub.2:yMeO;zF where x has a value of 0 to 0.2
y has a value of 0 to 0.2 z has a value of 0 to 0.10 and Me represents
at least one element, other than aluminum, phosphorus or silicon,
which is capable of forming an oxide in coordination with (AlO.sub.2)
and (PO.sub.2) oxide structural units in the molecular sieve, the
molecular sieve having, after calcination and in a hydrated state,
the X-ray diffraction lines of Table II.
2. The molecular sieve of claim 1 wherein Me is selected from the
group consisting of magnesium, manganese, cobalt, zinc and nickel.
3. A molecular sieve composition, as-synthesized, whose general
formula, in terms of mole ratios, is as follows: Al.sub.2O.sub.3:1.0.+-.0.2P.sub.2-
O.sub.5:0.5.+-.0.2 Q:xSiO.sub.2:yMeO:zF where x has a value of 0
to 0.2 y has a value of 0 to 0.2 Q is 4-dimethylaminopyridine,
z has a value of 0.02 to 0.50 and Me represents at least one element,
other than aluminum, phosphorus or silicon, which is capable of
forming an oxide in coordination with (AlO.sub.2) and (PO.sub.2)
oxide structural units in the molecular sieve.
4. The molecular sieve of claim 3 wherein Me is selected from the
group consisting of magnesium, manganese, cobalt, zinc and nickel.
5. The molecular sieve of claim 3 having, in an anhydrous state,
the X-ray diffraction lines of Table I.
6. The molecular sieve of claim 4 having, in an anhydrous state,
the X-ray diffraction lines of Table I.
7. A method of preparing a crystalline material comprising contacting
under crystallization conditions a reaction mixture comprising a
reactive source of aluminum, a reactive source of phosphorus, a
reactive source of fluoride and an organic templating agent comprising
4-dimethylaminopyridine.
8. The method of claim 7 wherein the reaction mixture further comprises
a reactive source of a metal selected from the group consisting
of magnesium, manganese, cobalt, zinc and nickel.
Molecular sieve description
FIELD OF INVENTION
[0001] The present invention relates in general to crystalline
aluminophosphate compositions, and more particularly to novel crystalline
aluminophosphates and metalloaluminophosphates of the molecular
sieve type, and to the methods of their preparation.
BACKGROUND OF THE INVENTION
[0002] Microporous crystalline aluminophosphate compositions having
open framework structures formed of AlO.sub.2 and PO.sub.2 tetrahedral
units joined by the sharing of the corner oxygen atoms and characterized
by having pore openings of uniform dimensions have heretofore been
disclosed in a number of publications, notably the specification
of U.S. Pat. No. 4310440 issued Jul. 7 1980 to S. T. Wilson
et al. The Wilson et al. aluminophosphates constitute a generic
class of non-zeolitic molecular sieve materials which are capable
of undergoing complete and reversible dehydration while retaining
the same essential framework topology in both the anhydrous and
hydrated state. By the term "essential framework topology"
or "essential framework structure" as used in the aforesaid
patent, and also in the present specification and claims, is meant
the spatial arrangement of the primary Al--O and P--O bond linkages.
Other microporous aluminophosphates which undergo structure rearrangements,
either reversibly or irreversibly, upon partial or complete dehydration
are also known, for example the minerals variscite and metavariscite
and certain of the synthetic metastable aluminophosphates reported
by F. D'Yvoire [Bull. Soc. Chim. France, 1762 (1961)]. Another class
of synthetic crystalline compositions contain framework tetrahedral
metal oxides of manganese, magnesium, cobalt, and/or zinc in addition
the AlO.sub.2 and PO.sub.2 tetrahedra. These are sometimes termed
metalloaluminophosphates or MAPO'S.
SUMMARY OF THE INVENTION
[0003] The present invention provides novel microporous crystalline
aluminophosphates ("ALPO's), aluminosilicophosphates ("APSO's")
metalloaluminophosphates ("MAPO's") and metalloaluminosilicophosphates
("MAPSO's") denominated SSZ-51 and the methods for its
preparation. SSZ-51 has an essential framework structure whose chemical
composition, expressed in terms of mole ratios after calcination,
is:
Al.sub.2O.sub.3:1.0.+-.0.2P.sub.2O.sub.5:xSiO.sub.2:yMeO;zF
[0004] where x has a value of 0 to 0.2 and y has a value of 0 to
0.2 z has a value of 0 to 0.10 and Me represents at least one element,
other than aluminum, phosphorus or silicon, which is capable of
forming an oxide in coordination with (AlO.sub.2) and (PO.sub.2)
oxide structural units in the molecular sieve (such as a divalent
metal). After calcination and in the hydrated form, SSZ-51 exhibits
an X-ray powder diffraction pattern which contains at least the
d-spacings set forth in Table II set forth hereinafter.
[0005] The framework structure of SSZ-51 consists of a building
unit which is essentially a double four ring (D4R) with one disconnected
(or ring-opened) edge. The fluoride ion used in synthesizing SSZ-51
is encapsulated within this building unit and forms a bridge between
two of the aluminum atoms. Each building unit is then connected
to four other identical building units, through two Al--O--P linkages
per unit. These building units can be linked together to form the
two structures, the SSZ-51 structure of this invention and a material
having the structure designated AFR (e.g., SAPO-40). The building
units can be joined in a "head-to-tail" fashion to form
chains running parallel to the c-direction. Chains are linked together
through four-rings to form undulating layers. The orientation of
successive chains in these layers is anti-parallel. This layer is
a building block of both SSZ-51 and AFR. The undulating layers can
be linked in two ways. If the layers are linked so that there is
inversion symmetry between the layers, this results in the SSZ-51
structure. If the layers are linked so that there is "mirror"
symmetry between the layers the resulting structure is that of AFR
(mirror symmetry here refers to the framework, i.e., excludes the
need for Al/P ordering).
[0006] SSZ-51 can be prepared by hydrothermal crystallization from
a reaction mixture containing in addition to water, a reactive source
of aluminum, phosphorus and fluoride and an organic templating agent
(sometimes referred to as a structure directing agent or "SDA")
which is 4-dimethylaminopyridine. Thus, the present invention further
provides a method of preparing a crystalline material comprising
contacting under crystallization conditions a reaction mixture comprising
a reactive source of aluminum, a reactive source of phosphorus,
a reactive source of fluoride and an organic templating agent comprising
4-dimethylaminopyridine. The reaction mixture may further comprise
a reactive source of a metal selected from the group consisting
of magnesium, manganese, cobalt, zinc and nickel.
[0007] Thus, the present invention provides a molecular sieve whose
chemical composition, expressed in terms of mole ratios of oxides
after calcination, is:
Al.sub.2O.sub.3: 1.0.+-.0.2P.sub.2O.sub.5:xSiO.sub.2:yMeO;zF
[0008] where x has a value of 0 to 0.2 y has a value of 0 to 0.2
z has a value of 0 to 0.10 and Me represents at least one element,
other than aluminum, phosphorus or silicon, which is capable of
forming an oxide in coordination with (AlO.sub.2) and (PO.sub.2)
oxide structural units in the molecular sieve, the molecular sieve
having, after calcination and in a hydrated state, the X-ray diffraction
lines of Table II.
[0009] The present invention further provides such a molecular
sieve wherein Me is selected from the group consisting of magnesium,
manganese, cobalt, zinc and nickel.
[0010] Further provided by the present invention is a molecular
sieve composition, as-synthesized, whose general formula, in terms
of mole ratios, is as follows:
Al.sub.2O.sub.3: 1.0.+-.0.2P.sub.2O.sub.5:0.5.+-.0.2Q:xSiO.sub.2:yMeO:zF
[0011] where x has a value of 0 to 0.2 y has a value of 0 to 0.2
Q is 4-dimethylaminopyridine, z has a value of 0.02 to 0.50 and
Me represents at least one element, other than aluminum, phosphorus
or silicon, which is capable of forming an oxide in coordination
with (AlO.sub.2) and (PO.sub.2) oxide structural units in the molecular
sieve.
[0012] The present invention also provides such an as-synthesized
molecular sieve wherein Me is selected from the group consisting
of magnesium, manganese, cobalt, zinc and nickel.
[0013] Also provided by the present invention is such an as-synthesized
molecular sieve having, in an anhydrous state, the X-ray diffraction
lines of Table I.
BRIEF DESCRIPTION OF THE FIGURES
[0014] FIG. 1 is an X-ray pattern (CuK.alpha.) of calcined and
hydrated SSZ-51.
[0015] FIG. 2 is a series of X-ray patterns (synchrotron, 0.704
Angstrom) illustrating the change in the pattern as calcined and
rehydrated SSZ-51 is dehydrated.
[0016] FIG. 3 is a series of X-ray patterns (synchrotron, 0.704
Angstrom) of as-made SSZ-51 as it is being calcined. The * indicates
berlinite peaks.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The novel microporous aluminophosphate (or MAPO) of the
present invention can be produced by hydrothermal crystallization
from a reaction mixture containing reactive sources of phosphorus
and aluminum and an organic templating agent (4-dimethylaminopyridine),
a source of HF and, optionally, additional divalent metals or sources
of silica. The preparative process typically comprises forming a
reaction mixture which in terms of mole ratios is:
Al.sub.2O.sub.3:1.+-.0.5P.sub.2O.sub.5: 0.5HF:0.3-1.5 Q:7-100H.sub.2O
[0018] where Q is the organic templating agent 4-dimethylaminopyridine.
The reaction mixture is placed in a reaction vessel inert toward
the reaction mixture and heated at a temperature of at least about
100.degree. C., preferably between 100.degree. C. and 300.degree.
C., until crystallized, usually a period of from 2 hours to 2 weeks.
The solid crystalline reaction product is then recovered by any
convenient method, such as filtration or centrifugation, washed
with water and dried in air at a temperature between ambient and
about 100.degree. C. In a preferred crystallization method, the
source of phosphorus is phosphoric acid, and the source of aluminum
is a hydrated aluminum oxide of the trade name Catapal, the temperature
is 150.degree. C. to 200.degree. C., the crystallization time is
from 2 to 7 days, and the ratio of compounds in the reaction mixture
is
Al.sub.2O.sub.3:0.8-1.2P.sub.2O.sub.5: 0.5HF:0.5-0.75Q:25-75H.sub.2O
[0019] The templating agent is 4-dimethylaminopyridine having the
structure 1
[0020] and is present in the reaction mixture in an amount of from
about 0.5 to 0.75 moles per mole of alumina. Additionally present
may be sources of divalent metals such as magnesium, manganese,
cobalt, zinc, nickel and so forth. In these instances it is anticipated
that these metals will replace Al in the lattice so the amount of
Al provided in the synthesis is reduced accordingly. Silica may
also be introduced into the reaction. Typically, silicon will replace
P in the lattice, so the amount of P provided in the synthesis is
reduced accordingly.
[0021] The template-containing as-synthesized form of SSZ-51 has
an essential framework structure whose chemical composition expressed
in terms of mole ratios is:
Al.sub.2O.sub.3:1.0.+-.0.2P.sub.2O.sub.5:0.5.+-.0.2 Q:xSiO.sub.2:yMeO:zF
[0022] where x, y, Me and z are as defined above. As-synthesized
SSZ-51 in an anhydrous state, has a characteristic X-ray powder
diffraction pattern which contains at least the d-spacings set forth
in Table I below.
1TABLE I Characteristic peaks of as-synthesized SSZ-51 d-spacing
Relative 2 Theta.sup.a (Angstroms) Intensity (%).sup.b 7.6 11.7
S 8.2 10.8 VS 13.9 6.4 VS 14.1 6.3 S 18.9 4.7 W 19.1 4.6 W-M 19.7
4.5 S 20.0 4.4 W-M 25.8 3.5 S 26.1 3.42 M .sup.a.+-.0.1 .sup.bThe
X-ray patterns provided are based on a relative intensity scale
in which the strongest line 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.
[0023] The complete X-ray powder diffraction pattern, including
actual relative intensities, for anhydrous, as-synthesized SSZ-51
is set forth in Table IA below.
2TABLE IA Peaks of as-synthesized SSZ-51 d-spacing Relative 2 Theta
(Angstroms) Intensity (%) 7.56 11.69 53.8 8.18 10.81 100.0 12.52
7.07 15.3 12.78 6.93 4.6 13.88 6.38 85.4 14.09 6.28 48.0 15.22 5.82
11.2 16.46 5.39 6.6 18.94 4.69 17.2 19.10 4.65 21.6 19.70 4.51 52.2
20.02 4.44 19.3 20.96 4.24 6.4 21.62 4.11 3.2 22.28 3.99 4.0 22.62
3.93 4.9 22.94 3.88 15.2 23.30 3.82 6.4 24.88 3.58 3.4 25.32 3.52
8.1 25.78 3.46 51.3 26.08 3.42 22.4 26.74 3.33 10.7 27.10 3.29 7.5
27.86 3.20 9.9 28.42 3.14 3.7 28.80 3.10 3.3 29.14 3.06 4.2 29.44
3.03 6.9 29.72 3.01 6.4 30.56 2.93 8.2 30.84 2.90 6.2 31.64 2.83
2.7 32.4 2.76 5.3
[0024] When the as-synthesized SSZ-51 compositions are calcined,
i.e., heated at a temperature sufficiently high, typically between
about 300.degree. C. and about 700.degree. C., or otherwise treated,
such as by chemical oxidation, to remove essentially all of the
organic templating agent present in the intracrystalline pore system
and then rehydrated, the composition has an X-ray powder diffraction
pattern which contains at least the d-spacings set forth in Table
II below:
3TABLE II Characteristic peaks of calcined and hydrated SSZ-51
d-spacing Relative 2 Theta (Angstroms) Intensity (%) 7.70 11.51
VS 8.08 10.9 VS 13.18 6.7 W 13.80 6.4 W 14.02 6.3 W 16.64 5.32 W
20.20 4.39 M 22.44 3.96 W 23.28 3.82 W 26.62 3.35 M 30.02 2.97 W-M
[0025] A complete X-ray powder diffraction pattern (synchrotron,
0.704 Angstrom), including actual relative intensities, for calcined,
rehydrated SSZ-51 is set forth in Table IIA below. Intensities were
determined by LeBail intensity extraction of the pattern.
4TABLE IIA Peaks of calcined, rehydrated SSZ-51 d-spacing Relative
2 Theta (Angstroms) Intensity (%) 3.45 11.7 100 3.63 11.1 63 5.81
6.95 12.2 5.87 6.87 2.7 6.19 6.52 9.9 6.52 6.19 13.2 6.98 5.78 1.3
7.27 5.54 1.9 7.92 5.10 2.3 8.61 4.69 10.7 8.68 4.65 5.7 9.00 4.48
23.2 9.36 4.32 14.8 9.55 4.23 4.6 10.02 4.03 3.1 10.36 3.90 10.2
10.45 3.87 2.1 11.57 3.49 10.9 11.76 3.43 7.4 11.87 3.40 15.6 12.29
3.29 1.9 12.38 3.26 5.0 12.67 3.19 5.9 12.78 3.16 2.9
[0026] The room temperature powder X-ray diffraction pattern of
SSZ-51 changes dramatically after calcination to remove the occluded
organic SDA and fluoride ions. There seems to be a distinct loss
of crystallinity, with diffraction peaks for the calcined sample
being much broader and less well defined than for the uncalcined
sample. It would appear that the calcination procedure has probably
resulted in some breakdown of the framework structure. However,
calcined SSZ-51 possesses appreciable microporosity (close to FAU-type
zeolites), and the density functional theory (DFT) measurements
indicate the likely presence of 12- and 8-rings. This is consistent
with the removal of fluoride and SDA while retaining the framework
structure intact. These two results are therefore seemingly at odds.
In order to follow the calcination process, variable temperature
powder X-ray diffraction data on the as-made sample was collected
in order to monitor structural changes as SSZ-51 is heated in air.
[0027] FIG. 3 shows the effect of temperature on the powder diffraction
pattern of the as-made sample of SSZ-51. The data were collected
at a synchrotron with a wavelength of about 0.704 Angstrom with
samples in rotating capillaries. Note the presence of peaks due
to berlinite (the AlPO analogue of quartz). As the material is heated
to 300.degree. C., there are only slight changes in the XRD pattern.
However, at 400.degree. C. there are dramatic changes in both the
peak positions and intensities as the SDA and fluoride are removed
from the structure. The shifts are readily apparent in the positions
of the (110), (200), and (310) reflections. This XRD pattern can
be indexed by a C-centered monoclinic cell with lattice parameters
of .alpha.=22.4 b=13.7 c=14.0 .beta.=98.5.degree. (as verified
by a LeBail profile fit). While the other lattice parameters show
little change, the .alpha. lattice parameter increases by 3.3%.
This change seems mostly due to the relaxation of the framework
as the fluoride bonds with the framework are broken.
[0028] After 400.degree. C., there is little variation in the pattern
due to structural changes in SSZ-51.
[0029] The good thermal stability of SSZ-51 is quite surprising
in that the material survives calcination to 800.degree. C. while
retaining a quite crystalline structure. This is at odds with the
room temperature XRD pattern, which shows a distinct loss of crystallinity.
This change in XRD pattern must then be due to the rehydration of
the framework rather than any inherent thermal instability of the
framework. On leaving the calcined SSZ-51 in moist air for a day
the broad diffraction pattern of FIG. 2 is again recorded. However,
on heating the sample to 100.degree. C., the diffraction pattern
reverts to that which we expect for a highly crystalline sample
of SSZ-51 with most of the expected reflections from the unit cell
distinctly visible. It would appear that the rehydration process
affects the crystallinity of the SSZ-51 framework markedly. A similar
effect is seen in the thermal treatment of SAPO-40 which has the
related AFR framework structure described above. Once again, the
structure of the framework is grossly changed by the addition of
water at room temperature, removing the long range order in the
structure and producing an X-ray diffraction containing broad Bragg
peaks. In both SSZ-51 and SAPO-40 this behavior is probably closely
linked to the addition of water to the framework aluminum atoms,
producing 5- and perhaps 6-coordinated aluminum atoms and so distorting
the structure away from that found for the dehydrated framework.
[0030] X-ray diffraction data was collected at a synchrotron source
with a wavelength of about 0.704 Angstrom. Interplanar spacings
(d) in Angstrom units are obtained from the position of the diffraction
peaks expressed as 2.theta. (theta) as observed on the strip chart
where theta is the Bragg angle. Intensities were determined from
the heights of diffraction peaks after subtracting background, "I.sub.o"
being the intensity of the strongest line or peak, and "I"
being the intensity of each of the other peaks.
[0031] As will be understood by those skilled in the art the determination
of the parameter 2 theta, irrespective of the technique employed,
is subject to both human and mechanical error, which in combination,
can impose an uncertainty of about 0.1.degree. on each reported
value of 2 theta. This uncertainty is, of course, also manifested
in the reported value of the d-spacings, which are calculated from
the 2 theta values. This imprecision is general throughout the art
and is not sufficient to preclude the differentiation of the present
crystalline materials from the compositions of the prior art. In
some of the X-ray patterns reported, the relative intensities of
the d-spacings are indicated by the notations VS, S, M, and W which
represent Very Strong, Strong, Medium, and Weak, respectively.
[0032] SSZ-51 exhibits surface characteristics which make it useful
as a catalyst or catalyst support in various hydrocarbon conversion
and oxidative combustion processes. SSZ-51 can be associated with
catalytically active metals, e.g., by framework substitution, by
impregnation, doping and the like, by methods traditionally used
in the art for the fabrication of catalyst compositions.
[0033] Further, SSZ-51 has a pore size of less than about 8 Angstroms
which makes SSZ-51 suitable for use as a molecular sieve for the
separation of molecular species. In addition, SSZ-51 is useful in
catalysts for hydrocarbon conversion reactions such as hydrocracking,
dewaxing and the like.
[0034] The following examples are provided to illustrate the invention
and are not to be construed as limiting thereof:
EXAMPLE 1
Synthesis of SSZ-51
[0035] SSZ-51 is prepared by combining 1.33 grams of a hydrated
aluminum oxide, a pseudo-boehmite phase comprising 75.1 weight percent
Al.sub.2O.sub.3 and 24.9 weight percent H.sub.2O, with a solution
of 2.2 grams of 85 wt % ortho-phosphoric acid (H.sub.3PO.sub.4)
and 9 grams of H.sub.2O. The resulting mixture is stirred until
a homogeneous mixture is observed. This mixture is then mixed with
0.22 grams of 50% HF and the resulting mixture stirred until homogeneous.
To the above mixture 0.90 grams of 4-dimethylaminopyridine (DMAP)
is added and then 0.06 grams of Cabosil M-5 amorphous fumed silica
and the resultant mixture is once again mixed until homogeneous.
The composition of reaction mixture in molar ratios is:
0.75DMAP:Al.sub.2O.sub.3:P.sub.2O.sub.5:0.5HF:0.1SiO.sub.2: 50H.sub.2O
[0036] The reaction mixture is sealed in a stainless steel pressure
vessel lined with polytetrafluoroethylene and heated in an oven
at 180.degree. C. at autogenous pressure for 50 hours. The solid
reaction product is recovered by filtration, washed with water and
dried in air at ambient temperature.
[0037] A portion of the solid reaction product is analyzed and
the following chemical analysis obtained:
1.26 wt % Si, 16.21 wt % Al, 17.75 wt % P and 1.10 wt % F
[0038] The organic content was not obtained in this analysis.
[0039] The solid reaction product is analyzed by X-ray powder diffraction
and found to be SSZ-51.
EXAMPLES 2-9
Synthesis of SSZ-51
[0040] In a manner similar to Example 1 SSZ-51 is prepared using
the starting materials and conditions shown in Table A below. Elemental
analysis for some of the products is shown in Table B below where
the numbers are weight percent.
5TABLE A Ex. Cabosil M-5 or Temp., Time No. H.sub.2O HF H.sub.3PO.sub.4
metal DMAP Al.sub.2O.sub.3.sup.1 .degree. C. (Days) 2 9 g 0.33 g
2.20 g 0.06 g.sup.2 0.90 g 1.33 g 180 2.5 3 9 g 0.33 g 2.20 g 0.12
g.sup.2 0.90 g 1.33 g 180 6 4 9 g 0.22 g 2.0 g Co.sup.3 1.20 g 1.33
g 180 2.5 5 9 g 0.33 g 2.2 g Co.sup.3 0.90 g 1.20 g 180 2.5 6 9
g 0.22 g 2.2 g Co.sup.3 0.90 g 1.26 g 180 2.5 7 9 g 0.22 g 2.2 g
Ni.sup.3 0.90 g 1.26 g 160 4 8 9 g 0.22 g 2.2 g Zn.sup.3 0.90 g
1.26 g 160 4 9 9 g 0.22 g 2.2 g Mg.sup.3 0.90 g 1.26 g 160 4 .sup.1Hydrated
aluminum oxide, 75.1 wt. % Al.sub.2O.sub.3 and 24.9 wt. % H.sub.2O
.sup.2Cabosil M-5 .sup.31 mmole added as nitrate salt
[0041]
6TABLE B Ex. No. Al P Si Co F Ni Zn Mg 1 16.1 17.75 1.26 1.10 5
15.95 19.72 1.91 2.33 7 14.94 18.79 2.12 3.08 8 14.57 20.06 1.74
1.73 9 16.92 20.20 1.46 0.34
COMPARATIVE EXAMPLE A
[0042] A reaction is conducted using the reactants and procedure
of Example 1 except that no HF was used. The crystalline product
is determined by X-ray analysis to be SAPO-5. This example demonstrates
that, when HF is left out of the reaction mixture, SAPO-5 is the
product rather than SSZ-51.
EXAMPLE 10
Unit Cell from Synchrotron Data
[0043] Data is collected on the product of Example 1 with the following
experimental parameters: A wavelength of 0.6875 Angstroms (Silicon
111 monochromator) is used in conjunction with Bruker-Nonius goniometer
equipped with a 1K CCD area detector and temperature controlled
to 150.degree. K. The determination is made that the crystalline
solid has, for a monoclinic, C2/c space group the following lattice
parameters:
[0044] a=21.759(3) Angstroms
[0045] b=13.8214(18) Angstroms, Beta=98.849(4) deg.
[0046] c=14.2237 (18) Angstroms.
EXAMPLE 11
Calcination of SSZ-51
[0047] The material from Example 1 is calcined in the following
manner. A thin bed of material is heated in a muffle furnace from
room temperature to 120.degree. C. at a rate of 1.degree. C. per
minute and held at 120.degree. C. for three hours. The temperature
is then ramped up to 540.degree. C. at the same rate and held at
this temperature for 5 hours, after which it is increased to 594.degree.
C. and held there for another 5 hours. A 50/50 mixture of air and
nitrogen is passed over the SSZ-51 at a rate of 20 standard cubic
feet per minute during heating.
EXAMPLE 12
Argon Adsorption Analysis
[0048] SSZ-51 has a micropore volume (t-plot) of 0.25 cc/gm based
on argon adsorption isotherm at 87.3 K recorded on ASAP 2010 equipment
from Micromeritics. The low-pressure dose was 2.00 cm.sup.3/g (STP)
with 15-s equilibration interval. 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). The DFT analysis also
shows that SSZ-51 has at least one large pore.
EXAMPLE 13
Calcination of SSZ-51
[0049] The product of Example 6 is calcined in the manner described
in Example 11.
EXAMPLE 14
Constraint Index Determination
[0050] The hydrogen form of the SSZ-51 of Example 13 is pelletized
at 2-3 KPSI, crushed and meshed to 20-40 and then >0.50 gram
is calcined at about 540.degree. C. in air for four hours and cooled
in a desiccator. 0.50 Gram is packed into a {fraction (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 800.degree.
F. (427.degree. C.), and a 50/50 (w/w) feed of n-hexane and 3-methylpentane
is introduced into the reactor at a rate of 8 .mu.l/min. Feed delivery
is made via a Brownlee pump. Direct sampling into a gas chromatograph
begins after 10 minutes of feed introduction. The Constraint Index
value is calculated from the gas chromatographic data using methods
known in the art. SSZ-51 has a Constraint Index of 0.4-0.5 at a
feed conversion of 40% at 800.degree. F. (427.degree. C.) after
10 minutes. The Constraint Index dropped with time on stream. The
Constraint Index values over this period continue to show large
pore molecular sieve behavior.
EXAMPLE 15
Hydrocracking of n-Hexadecane
[0051] A sample of SSZ-51 as prepared in Example 13 is impregnated
with Pd(NH.sub.3).sub.4(NO.sub.3).sub.2 salt using water and giving
a 0.5 wt. % Pd value with respect to the dry weight of the molecular
sieve sample. This slurry is stirred for 48 hours at room temperature.
After cooling, the slurry is filtered through a glass frit, washed
with de-ionized water, and dried at 100.degree. C. The catalyst
is then calcined slowly up to 482.degree. C. (900.degree. F.) in
air and held there for three hours.
[0052] The calcined catalyst is pelletized in a Carver Press and
crushed to yield particles with a 20/40 mesh size range. Sized catalyst
(0.5 g) is packed into a 1/4 inch OD tubing reactor in a micro unit
for n-hexadecane hydroconversion.
[0053] A balance of isomerization and cracking is observed as the
catalyst is taken through a regime of 30% conversion at 600.degree.
F. (315.degree. C.) to 90% at 667.degree. F. (353.degree. C.). The
cracking increases with temperature. The test is run at a WHSV of
1.55 at 1200 psig and without titration. Very little C.sub.1 and
C.sub.2 are observed and the iso/n ratios for C.sub.4 and larger
are indicative of large pore selectivity. |