Preparation of mesostructured lamellar zirconia

Article abstract of DOI:10.1039/a700974g

Mesostructured lamellar zirconia is synthesized by using anionic surfactants under hydrothermal conditions.

Full text of DOI:10.1039/a700974g

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Preparation of mesostructured lamellar zirconia
Yinyan Huang and Wolfgang M. H. Sachtler*
Ipatieff Laboratory, Center for Catalysis and Surface Science, Northwestern University, Evanston, IL 60201, USA
Mesostructured lamellar zirconia is synthesized by using
anionic surfactants under hydrothermal conditions.
to inaccurate results. Schu¨th has shown that a highly resolved
XRD pattern can be consistent with a chaotic structure.12
Therefore, the present work mainly employs TEM to identify
the structure of the materials. Fig. 2 shows the TEM image of
mesostructured zirconia obtained by using n-C16H33SO3Na
surfactant. The lamellar structure is clearly visible. The distance
between two layers is estimated to be ca. 41 Å. This is
consistent with the value obtained from XRD.
Since the discovery by scientists at Mobil of the mesoporous
aluminosilicate (MCM-41),1,2 much attention has been paid not
only to mesoporous aluminosilicates, but also to mesoporous
oxides of other metals. Many mesoporous transition-metal
oxides have been obtained. Huo et al.3 and Ciesla et al.4 report
the syntheses of mesostructured oxides of Fe, Mn, Zn, Co, Ni,
Al, Sb, W by interaction of a soluble metal solution and an
anionic surfactant. Unfortunately, attempts to remove the
template used for synthesis, either by leaching or by calcination,
have led to the collapse of the mesostructure. Recently the
syntheses of mesoporous TiO2, Nb2O5 and ThO2 with hexago-
nal pore arrangements and amorphous pore walls have been
reported.5–7 As for mesostructured zirconia, several papers
report that this material can only be obtained with amorphous
walls8,9 and irregular pore arrangement. The mesoporosity is,
however, lost upon crystallization of the zirconia. Another
paper claims the synthesis of mesoporous zirconia with regular
pore arrangement based on small-angle XRD.10 Mesoporous
lamellar zirconia was also prepared by a route using neutral
amines, but the mesostructure was lost when the samples were
calcined to remove the surfactant.11 The synthesis of mesopor-
ous zirconia using a neutral amine template that was subse-
quently extracted with ethanol has been reported by us;
although no regular pore structure has been obtained, the
mesoporosity of this material can be maintained up to 700 °C if
the tetragonal modification of zirconia is stabilized by sulfation.
Here, we report the synthesis of mesostructured lamellar
zirconia, by using soluble zirconium chloride and an anionic
surfactant.
The same lamellar TEM image is found with material
obtained using n-C16H33SO2Cl as the template. Incorporation of
Pt does not change the mesostructure of the materials.
250
(a) ZrOCl + C
2
H
SO Na
3
16 33
200
150
100
50
(b) ZrOCl + C
2
H
SO Cl
2
16 33
Lamellar zirconia is obtained by hydrothermal reaction. In a
typical synthesis process, 1.5 g ZrOCl2 was first dissolved in 10
ml water. 1.26
g
of sodium 1-hexadecanesulfonate
(n-C16H33SO3Na) was then dissolved in 10 ml water and mixed
with the ZrOCl2 solution under stirring. The surfactant/
zirconium molar ratio is ca. 0.5 and the mixture has a pH of ca.
6. Stirring was continued for 30 min; the mixture was then
sealed in a polyethylene bottle and heated at 90 °C for 48 h
before final filtering, washing and drying in air.
0
0
2
4
6
8
10
2q / °
Fig. 1 Small-angle XRD patterns of mesostructured zirconia synthesized by
using surfactant n-C16H33SO3Na (a) and n-C16H33SO2Cl (b)
Besides sodium 1-hexadecanesulfonate, 1-hexadecanesulfo-
nyl chloride (n-C16H33SO2Cl) was also used as surfactant for
the synthesis of mesostructured zirconia, using the same
procedure. In some cases, some Pt(NH3)4(NO3)2 was added to
a zirconyl chloride solution before mixing it with the surfactant
solution. The Pt loading is ca. 1 mass% based on the amount of
ZrO2.
The materials have been characterized by small-angle XRD
and TEM. Fig. 1(a) and (b) show the small-angle XRD patterns
of mesostructured zirconias synthesized using either the
surfactant n-C16H33SO3Na or n-C16H33SO2Cl. Their XRD
patterns are very similar. The peak at 2q = 2° clearly indicates
the existence of some mesostructure. The peaks at higher
diffraction angles are not well resolved. In view of the
inaccuracy of the XRD pattern, a d value of ca. 40 Å is
estimated for the first peak.
Though many authors use small-angle XRD to determine the
symmetry of the mesostructure, this procedure sometimes leads
Fig.
n-C16H33SO3Na
2 TEM image of mesostructured zirconia synthesized with
Chem. Commun., 1997
1181

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The materials were also analysed by thermal gravimetry
(TG). As shown in Fig. 3, the surfactant is oxidized in an O2
atmosphere at ca. 275 °C. A strong exothermic effect is
observed at that temperature. The total mass loss is due to
desorption of occluded materials in addition to oxidation of the
surfactant. The mass loss corresponding to the oxidation of
surfactant is about 50% of the total mass. Based on the TG
results, a Zr/surfactant molar ratio of 1.5 is estimated. This is
higher than expected for the charge balance of ZrO2+ with
n-C16H33SO32. Apparently considerable quantities of water
and other species are included in the material.
molecule’. This composite molecule has a low solubility in
water and tends to reassemble, forming an ordered structure.
Although considerable effort was made to maintain the
mesostructure by cautiously removing the surfactant, these
attempts failed. Leaching of the material synthesized from
n-C16H33SO3Na with an ammonia–ethanol mixture did not
work either, whereas such treatment with the material from
n-C16H33SO2Cl leads to the gelation of the original material.
Calcination of the materials in air at 500 °C for 6 h results in
the collapse of the lamellar structure and the formation of
tetragonal zirconia. The characteristic small-angle diffraction
peak is lost. Upon calcining these materials in a flow of oxygen
(100 ml min21) at 300 °C for 2 h at low ramping rate (0.5 °C
min21), XRD analysis shows that the lamellar structure
collapses and amorphous zirconia is obtained. TEM confirms
that the material contains mainly amorphous zirconia particles
and some small particles of tetragonal zirconia. In the case of
the Pt-containing materials, highly dispersed Pt metal particles
are formed. Fig. 4 shows rather uniform Pt particles dispersed
on zirconia.
As n-C16H33SO3Na is dissolved in water, the negative
n-C16H33SO32 ion is formed. The anion can also be formed by
hydrolysis of n-C16H33SO2Cl. The surfactant anion will react
with the ZrO2+ cation to form a ‘cation–anion composite
120
100
80
500
400
300
200
100
0
We gratefully acknowledge financial support from the
director of the Chemistry Division, Basic Energy Sciences, US
Department of Energy; Grant DE-FGO2-87ER13654 and a
grant-in aid from Shell Development Company. We thank Dr
Xiandong Wang for helping in TG analysis and Dr Timothy
J. McCarthy and Dr Taeghwan Hyeon for taking the TEM
images.
T
60
40
Footnote
* E-mail: wmhs@nwu.edu
20
0
50
100
150
t / min
200
250
References
Fig.
3 TG profile of mesostructured zirconia synthesized with
1 C. T. Kresge, M. E. Leonowicz, W. J. Roth, J. C. Vartuli and J. S. Beck,
Nature, 1992, 359, 710.
n-C16H33SO3Na registered in a flow of oxygen of 20 ml min21
2 J. S. Beck, J. C. Vartuli, W. J. Roth, M. E. Leonowicz, C. T. Kresge,
K. D. Schmitt, C. T.-W. Chu, D. S. Olson, E. W. Sheppard,
S. B. McCullen, J. B. Higgins and J. L. Schlenker, J. Am. Chem. Soc.,
1992, 114, 10 834.
3 Q. Huo, D. I. Margolese, U. Ciesla, D. G. Demuth, P. Feng, T. E. Gier,
P. Sieger, A. Firouzi, B. F. Chmelka, F. Schu¨th and G. D. Stucky, Chem.
Mater., 1994, 6, 1176.
4 U. Ciesla, D. Demuth, R. Leon, P. Petroff, G. Stucky, K. Unger and
F. Shu¨th, J. Chem. Soc., Chem. Commun., 1994, 1387.
5 D. M. Antonelli and J. Y. Ying, Angew. Chem., Int. Ed. Engl., 1996, 35,
426.
6 D. M. Antonelli, A. Nakahira and J. Y. Ying, Inorg. Chem., 1996, 35,
3126.
7 D. M. Antonelli and J. Y. Ying, Chem. Mater., 1996, 8, 874.
8 M. J. Hudson and J. A. Knowles, J. Mater. Chem., 1996, 6, 89.
9 U. Ciesla, S. Schacht, G. D. Stucky, K. K. Unger and F. Schu¨th, Angew.
Chem., Int. Ed. Engl., 1996, 35, 541.
10 J. S. Reddy and A. Sayari, Catal. Lett., 1996, 38, 219.
11 N. Ulagappan, Neeraj, B. V. N. Raju and C. N. R. Rao, Chem. Commun.,
1996, 2243.
12 F. Schu¨th, Ber. Bunsen-Ges. Phys. Chem., 1995, 99, 1306.
Fig. 4 TEM image of Pt containing mesostructured zirconia by using
n-C16H33SO3Na as surfactant, after calcination at 300 °C in a flow of
oxygen of 100 ml min21
Received in Columbia, MO, USA, 11th February 1997; Com.
7/00974G
1182
Chem. Commun., 1997