Characterization of UTD-1
J. Am. Chem. Soc., Vol. 119, No. 36, 1997 8475
Scheme 1
the methods described in ref 23 and calcined as above. Calcined UTD-1
(2.61 g) was suspended in 175 mL water in a polypropylene bottle. A
total of 3.48 g of aluminum nitrate nonahydrate was dissolved into the
slurry, and the solution was heated for 2.5 days at 90 °C. Upon
removing the plastic bottle from the oven, the solution is pink (dissolved
cobalt in acidic solution) and the solids are white. The solids are
filtered, washed with 100 mL of 0.01 N HCl, and washed with distilled
water. Chemical analyses show a SiO
2
/Al
2
O
3
ratio ∼70. The
aluminum-containing samples of UTD-1 will be denoted Al-UTD-1.
Analytical. Synchrotron X-ray diffraction data were obtained at
the X7A beam line of the Synchrotron Light Source, Brookhaven
National Laboratory. The sample, after calcination and removal of the
cobalt oxide by acid treatment, was dried at 200 °C for 12 h and packed
in a 1 mm glass capillary. The data were collected at room temperature
from 2-65° 2θ with a step scan of 0.01° and a wavelength λ ) 1.2513
Å. Room temperature powder X-ray diffraction (XRD) patterns were
recorded on a Scintag XDS 2000 diffractometer equipped with a liquid
nitrogen-cooled germanium detector, Cu KR radiation λ ) 1.54184 Å
and a Bragg-Brentano geometry.
by AlPO4-8 (14MR), cloverite (20MR), JDF-20 (20MR),17
1
5
16
1
8
19
ULM-5 (16MR), ULM-16 (16MR), and two new vanadium
phosphates with 24MR cages.2
0,21
However, the practical
application of these phosphate-based, extra-large-pore materials
has been hampered by their poor thermal and/or hydrothermal
stability. UTD-1, on the other hand, shows the typical high
The thermal and hydrothermal stability of UTD-1 were investigated
by in situ X-ray powder diffraction. The samples were mounted as
thin films on a platinum-rhodium alloy sample-holder/strip-heater
within an Edmund Buhler high-temperature XRD chamber. The
chamber was evacuated and refilled with the flow gas three times prior
to establishing the steady flow under which the data were collected.
The flow gas for the thermal stability experiments was dry nitrogen.
Nitrogen gas, bubbled through distilled water maintained at room
temperature, was used for the hydrothermal experiments. The gas flow
1
2
thermal and hydrothermal stability of high-silica zeolites.
Because UTD-1 is the first extra-large-pore zeolite, detailed
investigation of its physicochemical properties are merited. Here
we present a detailed characterization of UTD-1 using synchro-
tron X-ray powder diffraction, electron diffraction, high-
resolution transmission electron microscopy, scanning electron
microscopy, solid-state NMR spectroscopy, adsorption studies,
and thermal/hydrothermal stability investigations. The relation-
ship between the geometry of the structure-directing agent (bis-
pentamethylcyclopentadienyl)cobalt(III)), [(Cp*)2Co] , and the
shape and size of the pores is investigated using energy
minimization calculations. The acid-catalyzed properties of
UTD-1 are investigated using the isomerization of xylenes as a
test reaction.
-1
rates were approximately 0.5 L min . The temperature controller was
calibrated to within 10 °C using the melting points of NaCl and KNO
3
as the standards. Samples of calcined and HCl-washed UTD-1 were
mounted on the sample holder in thicknesses varying from ap-
proximately 0.5 mm to 1 mm. The diffraction scans were taken from
+
(
2
-51° 2θ with a 0.04 step size and 5 s count periods. In both thermal
and the hydrothermal experiments, the temperature was ramped at 10
-1
°
C min , and held at the designated temperature for 15 min before
the scan. X-ray diffraction patterns were recorded at room temperature,
00, 400, 500, 600, 800, 900, 1000 °C and finally again at room
2
Experimental Section
temperature.
Scanning electron microscopy (SEM) images were recorded on a
Camscan 2-LV electron microscope operating with an acceleration
voltage of 15 kV. Thermogravimetric analysis (TGA) was carried out
on a Du Pont 951 thermogravimetric analyzer in flowing dry argon
Synthesis. The samples of UTD-1 were synthesized as previously
12,9
reported, using bis(pentamethylcyclopentadienyl)cobalt(III) hydrox-
ide, (Cp*)
2
Co OH, as a structure-directing agent.2
2
To eliminate the organometallic structure-directing agent from the
pores, the as-made UTD-1 (yellow) was heated in a furnace in flowing
nitrogen containing a few percent of air. The solid was heated at 1 °C
-1
using a constant heating rate of 1 K min . Chemical composition
analyses were carried out at Galbraith Laboratories, Knoxville, TN.
The adsorption capacities of UTD-1, SSZ-24, zeolite L, and zeolite
Y were measured at room temperature using a Cahn C-2000 balance
-
1
min to 540 °C and maintained at this temperature for 4 h; the
-
1
temperature was increased again at 0.5 °C min to 600 °C, and held
at this temperature for another 4 h. Finally, the sample was cooled to
room temperature over several hours in the furnace. The product has
a blue color at this point. After the calcination step, the product contains
cobalt oxide occluded in the pores and in the external surface of the
crystals (see below). This oxide is eliminated by an aqueous acid
treatment (12 N HCl and then 7 N HCl) as previously reported.12 The
samples used here for adsorption studies, X-ray powder diffraction,
electron microscopy, and NMR spectroscopy have been treated in this
manner before characterization.
coupled with a computer via an ATI-Cahn digital interface. Several
24
“
plug gauge” molecules with various kinetic diameters are used. The
adsorbate vapors are delivered from the liquid phase and the partial
pressure P/P
0
() 0.15-0.4) of the organic adsorbate was adjusted using
a temperature controlled thermostat. Prior to the adsorption experiment,
-3
the calcined samples are dehydrated at 615 K under a vacuum of 10
Torr for 5 h. The pore volumes are given on the basis of the weight
gains of the adsorbents upon adsorption, and the densities of the liquid
adsorbates at room temperature, i.e., assuming that the adsorbates in
the sample pores have the same density as the liquid state.
For the catalytic tests, the incorporation of aluminum in the samples
was carried out as follows: A sample of UTD-1 was prepared using
Solid-state NMR spectroscopy was performed on a Bruker AM 300
spectrometer equipped with a high power assembly for solids. Samples
2
9
were packed into 4 and 7 mm ZrO
59.63 MHz) single-pulse experiments were performed at spinning rates
of 2.7-3.5 kHz, pulse widths of 4 µs (40° pulse), and recycle delays
2
rotors and spun in air. Si NMR-
(
15) Dessau, R. M.; Schlenker, J. L.; Higgins, J. B. Zeolites 1990, 10,
22-524.
16) Estermann, M.; McCusker, L. B.; Baerlocher, C.; Merrouch, A.;
Kessler, H. Nature 1991, 352, 320-323.
17) Jones, R. H.; Thomas, J. M.; Chen, J. S.; Xu, R. R.; Huo, Q. S.; Li,
(
5
(
1
29
1
of 10-100 s. H- Si CPMAS NMR spectra were measured with H
(
1
1
decoupling at spinning rates of 2.5-3 kHz using a 7 ms H pulse ( H
S. G.; Ma, Z. J. Solid State Chem. 1993, 102, 202-208.
9
0°), 29Si contact times of 5-15 ms, and recycle times of 3 s. Si
29
(
(
(
18) Loiseau, T.; Ferey, G. J. Solid State Chem. 1994, 111, 403-415.
19) Loiseau, T.; Ferey, G. J. Mater. Chem. 1996, 6, 1073-1074.
20) Khan, M. I.; Meyer, L. M.; Haushalter, R. C. Chem. Mater. 1996,
NMR chemical shifts are referenced to external standard of tetrakis-
(trimethylsilyl)silane (downfield resonance at -10.05 ppm relative to
1
8
, 43-53.
tetramethylsilane). H NMR (300.15 MHz) spectra were measured at
(21) Schindler, M.; Joswig, W.; Baur, W. H. Z. Anorg. Allg. Chem. 1997,
6
23, 45-54.
(23) Zones, S. I.; Nakagawa, Y. Microporous Mater. 1994, 2, 543-
555.
(
22) Balkus, K. J.; Gabrielov, A. G.; Zones, S. I.; Chan, I. Y. In Synthesis
of Microporous Materials, Zeolites, Clays and Nanocomposites; Kessler,
H., Occelli, M., Eds.; Marcel Dekker: New York, 1996.
(24) Breck, D. W. Zeolite Molecular SieVes: Structure, Chemistry and
Use; Wiley: New York, 1974.