Catalytic activity of FSM-16 for photometathesis of propene

Article abstract of DOI:10.1039/a607406e

Mesoporous silica (FSM-16) catalyses metathesis of propene under photoirradiation at a higher activity than amorphous silica whereas microporous silica crystals (silicalite-1) do not catalyse the reaction.

Full text of DOI:10.1039/a607406e

View Article Online / Journal Homepage / Table of Contents for this issue
Catalytic activity of FSM-16 for photometathesis of propene
Hisao Yoshida,* Koichi Kimura, Yoshitaka Inaki and Tadashi Hattori
Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Nagoya 464-01, Japan
Mesoporous silica (FSM-16) catalyses metathesis of propene
under photoirradiation at a higher activity than amorphous
silica whereas microporous silica crystals (silicalite-1) do not
catalyse the reaction.
The N2 adsorption isotherms of AMS and FSM-16 were of
type IV indicating the presence of mesopores; isotherms of
silicalite-1 and DM were of type I, also suggesting microporous
structures.
Table 1 shows the catalytic activities of the samples
evacuated at 873 K for propene metathesis under photoirrad-
iation. AMS catalysed the metathesis reaction quite slowly, the
activity roughly corresponding to that reported previously.5 By
contrast, FSM-16 showed a much higher metathesis activity
than AMS. It should be noted that FSM-16 seemed to exhibit a
higher specific activity than AMS. This is because the ratio of
catalytic activity of FSM-16 to that of AMS is larger than the
ratio of BET surface areas (1170 and 580 m2 g21 for FSM-16
and AMS, respectively). The C2/C4 ratio on FSM-16 was close
to unity, indicating the metathesis reaction proceeded se-
lectively. In contrast, silicalite-1 showed no activity, indicating
its microporous structure is of no advantage under the reaction
conditions. DM also give no gaseous products and judging from
Mesoporous silica materials such as MCM-411,2 and FSM-163,4
attract a great deal of attention as new materials and many
applications are expected. Although the application of these
materials for catalysis has been widely studied, attention has
also been paid to the generation of catalytic activity through the
introduction of other metal ions into the silica lattice, but not to
the catalytic activity of unmodified mesoporous silica.
Here, we show that unmodified mesoporous silica (FSM-16)
has a higher catalytic activity in the photometathesis of propene
than does amorphous silica which was recently found to be
catalytically active in this reaction.5 To elucidate structural
factors of mesoporous silica in this reaction, we compare the
catalytic activities of other forms of SiO2; amorphous silica,
microporous crystalline silica (silicalite-1)6 and high-silica
zeolite (dealuminated mordenite).
(e)
Amorphous silica (AMS) was prepared by the sol–gel
method7 by hydrolysis of tetraethylorthosilicate (TEOS) fol-
lowed by calcination at 773 K for 5 h. FSM-16 was prepared
essentially in the same manner as described by Inagaki et al.3,4
except that hexadecyltrimethylammonium bromide was used as
a template and the resulting material was calcined at 873 K in an
N2 atmosphere for 1 h and subsequently in air for 5 h. Silicalite-
1 was synthesized from TEOS and tetrapropylammonium
bromide (TPABr) by hydrothermal synthesis (433 K, 24 h)
followed by washing, drying and calcination at 823 K.
(d)
Dealuminated mordenite (DM, SiO2/Al2O3
= 328) was
obtained by extraction (123) of aluminium using 8 m HCl at
333 K for 24 h8 from JRC-Z-HM15 (a reference catalyst,9,10
Catalysis Society of Japan). The structures of the samples were
confirmed by XRD and N2 adsorption–desorption isotherms.
Photocatalytic conversion of propene was carried out under
irradiation for 1 h using a 250 W Hg lamp in a closed static
system (120 ml; propene 100 mmol) at room temperature. The
powdered catalyst (200 mg) was spread on the flat bottom (12
cm2) of a quartz reactor irradiated from beneath. Pretreatment of
catalyst was performed at 873 K (or 1073 K) in air for 2 h and
in the presence of 100 Torr oxygen for 1 h, followed by
evacuation at the same temperature. After 1 h reaction, products
and unreacted propene were collected with a liquid-N2 trap
when the catalyst was under irradiation, and were analysed by
GC.
The XRD patterns of the samples pretreated at 873 K and that
of silicalite-1 pretreated at 1073 K are shown in Fig. 1. AMS (a)
showed a very broad diffraction peak at 2q ca. 22°, indicating
its amorphous nature. The FSM-16 sample (b) exhibited low-
angle diffraction peaks at 2q 2.36, 4.06 and 4.68° and a very
broad diffraction peak at 2q ca. 23° as reported,3,4 indicating
that this material has ordered hexagonal mesopores with XRD
amorphous walls. Silicalite-1 (c) and DM (d) were clearly
assigned by comparison with their published structures.6,11 The
structures of AMS, FSM-16 and DM were essentially un-
changed upon calcination at 1073 K, while silicalite-1 calcined
at 1073 K (e) gave an XRD pattern resembling that of
amorphous silica.
(c)
× 0.2
(b)
(a)
20
0
10
30
2θ / °
Fig. 1 XRD patterns of porous silica materials: (a) amorphous silica (AMS),
(b) FSM-16, (c) and (e) silicalite-1 and (d) dealuminated mordenite (DM).
Samples (a)–(d) were calcined at 873 K and (e) at 1073 K. The intensity of
the low-angle region of (b) is reduced to 1/5.
Chem. Commun., 1997
129

View Article Online
Table 1 Results of tests for propene photometathesis on silica materials
Yield (%)
Conv. (%)
to
metathesis
Pretreatment
temperature/K
C2/C4
ratio
a
Sample
C2
trans-C4
cis-C4
1-C4
Adsorbed
873
AMS
1.4
8.2
0.0
1.0
5.7
0.0
0.7
2.8
0.0
0.0
4.4
4.7
0.0
0.0
0.0
0.3
0.0
0.0
0.0
0.4
0.0
0.0
1.0
5.8
2.3
100.0
2.0
5.6
3.1
16.9
0.0
0.82
0.94
—
FSM-16
Silicalite-1
DM
0.0
0.0
0.0
—
1073
AMS
16.8
16.2
0.0
11.8
12.0
0.0
33.0b
33.3b
0.0
1.04
0.95
—
FSM-16
Silicalite-1
DM
1.3
98.7
0.0
0.0
0.0
—
a C2 = ethene, C4 = butene. b Conversions on amorphous silica and FSM-16 reached equilibrium under the reaction conditions.5
the colour of DM after reaction, propene appears to have been
adsorbed and polymerized on acid sites of DM.
Upon evacuation at higher temperature (1073 K), the
activities of AMS and FSM-16 greatly increased, while DM
produced no gaseous products, as shown in Table 1. Activation
of amorphous silica upon evacuation at high temperature is in
agreement with a previous report.5
Upon evacuation at 1073 K the zeolite structure of silicalite-1
was destroyed and became XRD amorphous (BET surface area
7.5 m2 g21). This amorphous sample gave no metathesis
products even after 30 h reaction.
higher photocatalytic activity for propene metathesis than
amorphous silica. The key point is that FSM-16 has many
hydroxy groups on the amorphous walls which constitute the
hexagonal mesopore structure. The active sites are proposed to
be produced by desorption by hydroxy groups from the
amorphous surface of silica.
We thank Mr T. Abe, K. Nishi, T. Ishikura (Nagoya Univ.),
S. Inagaki and Dr Y. Fukushima (Toyota Central R & D Labs.,
Inc.) for their help in the preparation of samples.
It is suggested from the results on the catalyst samples
evacuated at 873 K that an amorphous phase of silica might be
necessary for photometathesis on silica since reaction did not
proceed on microporous crystalline silica, but only on amor-
phous silica (AMS) and on FSM-16 whose walls are amor-
phous.2,12 The results on the catalysts evacuated at 1073 K,
however, indicated that catalytic activity is governed by the
other factors, since amorphous samples produced by evacuation
of silicalite-1 showed no activity.
Another distinguishable factor between these samples is the
concentration of surface hydroxy groups: microporous crystals
have few hydroxy groups, while amorphous silica surfaces such
as AMS and FSM-16 would possess a large amount of hydroxy
groups, The increase of activity of AMS and FSM-16 evacuated
at higher temperature indicates that this process produces active
sites on the samples. Therefore it is suggested that sites
produced by desorption of hydroxy groups would regulate the
activity. For silicalite-1, there are only a small number of
hydroxy groups prior to evacuation. Therefore, silicalite-1
evacuated at high temperature possesses few active sites,
despite its amorphous surface.
References
1 C. T. Kresge, M. E. Leonowicz, W. J. Roth, J. C. Vartuli and J. S. Beck,
Nature, 1992, 359, 710.
2 J. S. Beck, J. C. Vartuli, W. J. Roth, M. E. Leonowicz, C. T. Kresge,
K. D. Schmitt, C. T.-W. Chu, D. H. Olson, E. W. Sheppard,
S. B. McCullen, J. B. Higgins and J. L. Schlenker, J. Am. Chem. Soc.,
1992, 114, 10834.
3 S. Inagaki, Y. Fukushima and K. Kuroda, J. Chem. Soc., Chem.
Commun., 1993, 680.
4 S. Inagaki, A. Koiwai, N. Suzuki, Y. Fukushima and K. Kuroda, Bull.
Chem. Soc. Jpn., 1996, 69, 1449.
5 H. Yoshida, T. Tanaka, S. Matsuo, T. Funabiki and S. Yoshia, J. Chem.
Soc., Chem. Commun., 1995, 761.
6 E. M. Flanigen, J. M. Bennett, R. W. Grose, J. P. Cohen, R. L. Patton,
R. M. Kirchner and J. V. Smith, Nature, 1978, 271, 512.
7 S. Yoshida, T. Matsuzaki, T. Kashiwazaki, K. Mori and K. Tarama,
Bull. Chem. Soc. Jpn., 1974, 47, 1564.
8 A. Satsuma, T. Ishikura, T. Shimizu, M. Niwa, T. Hattori and
Y. Murakami, Kagaku Kogaku Ronbunshu, 1995, 21, 1120.
9 T. Hattori, H. Matsumoto and Y. Murakami, Stud. Surf. Sci. Catal.,
1987, 31, 815.
10 T. Uchijima, in Catalytic Science and Technology, ed. S. Yoshida, N.
Takezawa and T. Ono, Kodansha, VCH, Tokyo, 1991, vol. 1, p. 393.
11 M. M. J. Treacy, J. B. Higgins and R. von Ballmoos, Zeolites, 1996, 16,
323.
There are two possibilities why FSM-16 exhibits higher
activity than AMS. One is that FSM-16 has a larger number of
surface hydroxy groups than AMS. The second is that the nature
of the active sites differs from that of AMS as a consequence of
the characteristic walls of FSM-16 which consist of double SiO4
tetrahedral layers.13
12 C.-Y. Chen, H.-X. Li and M. E. Davic, Microporous Mater., 1993, 2,
17.
13 S. Inagaki, Y. Sakamoto, Y. Fukushima and O. Terasaki, Chem. Mater.,
1996, 8, 2089.
In conclusion, the catalytic activity of unmodified mesopo-
rous silica (FSM-16) has been investigated. FSM-16 exhibits
Received, 30th October 1996; Com. 6/07406E
130
Chem. Commun., 1997