Synthesis, Characterization and Catalytic Properties of TBS-2 Zeolites

Article abstract of DOI:10.1039/a804836c

Titanium and B co-substituted silicate-2 zeolites were characterized using XRD, FT-1R and NH₃-TPD, and the TBS-2s bifunctional catalytic properties as oxidative and acidic catalysts were investigated using the epoxidation of styrene and rearrangement of styrene oxide.

Full text of DOI:10.1039/a804836c

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764 J. CHEM. RESEARCH (S), 1998
J. Chem. Research (S),
1998, 764±765$
Synthesis, Characterization and Catalytic Properties
of TBS-2 Zeolites$
Zaihui Fu,* Dulin Yin, Donghong Yin, Luxi Zhang and Youyu Zhang
Institute of Fine Catalysis & Synthesis, Hunan Normal University, Changsha, 410081, P.R. China
Titanium and B co-substituted silicate-2 zeolites were characterized using XRD, FT-IR and NH3-TPD, and the TBS-2's
bifunctional catalytic properties as oxidative and acidic catalysts were investigated using the epoxidation of styrene and
rearrangement of styrene oxide.
Co-incorporation of Ti and trivalent metal ions such as B3‡
,
S-2 framework must be appropriate, the use of excessive
H2O2 or H3BO3 will obviously inhibit such incorporation.
The addition of 10% aq. TMAOH not only avoids serious
gelation, but also eciently enhances the incorporation of
boron (samples 6 and 7).
Al3‡, Ga3‡, or Fe3‡ in MFI and MEL structures to modify
their catalytic properties has been reported recently.1±6
However, details of the synthesis, characterization and cata-
lytic properties of the co-incorporated zeolites are sparse.
In the present work, we report the synthesis, characteriz-
ation and catalytic properties of TSB-2 zeolites.
NH3-TPD was used to measure the acidic properties
of these zeolites. The amounts of ammonia desorbed
from these zeolites and the maximum temperatures are
summarized in Table 1. There is only a desorption peak
for the all samples with a desorption temperature range of
383±573 K. The NH3 uptakes on the greater part of TBS-2
zeolites are higher than on TS-2 and BS-2; the two TBS-2
samples (samples 1 and 5) and BS-2 have lower NH3
uptakes, which is attributed to the decrease in the frame-
work Ti and B bands in these samples. The maximum tem-
peratures of NH3 desorption on TBS-2 and BS-2 zeolites
are 20±30 K higher than that of TS-2. These results show
that all these zeolites have weak acidic properties, and the
incorporation of boron in TS-2 can enhance both the
number and strength of its acid sites.
The observed XRD patterns for calcined TBS-2 zeolites,
which are well crystallized, show no line broadening and
match well those of TS-2, BS-2 and S-2, strongly suggest
that Ti and B are simultaneously incorporated into the
MEL structure. The unit cell volume of TS-2 (Table 1) is
larger than that of pure S-2 and consistent with many
reports.7 However, that of TBS-2 is smaller than that of
pure S-2 and larger than that of BS-2. This is due to the
replacement of the framework Si by the smaller B3‡ ions,
which can cause S-2 framework contraction. A decrease in
the unit cell parameters should con®rm that boron has been
successfully incorporated into the framework of TS-2. The
1
IR bands at 960 and 1380 cm are used as ®ngerprints of
Ti and B incorporation into the S-2 framework.7,8 The
absence of any new IR features in TBS-2 other than frame-
work Ti and B bands may indicate that, despite the presence
of the two elements in the same crystallites, there are no
mixed Ti±O±B sites in the framework.
Increasing the H2O2:SiO2 ratio from 0.13 to 0.26:1
(corresponding to samples 2 and 1) will obviously cause a
decrease in the framework B band, but varying this ratio in
the range 0.13±0.08 will not a€ect the two framework bands
(samples 2 and 3). However, when increasing B2O3:SiO2
from 0.05 to 0.10:1 (samples 2, 3, 4 and 5) the framework B
band is not obviously increased, and the framework Ti band
is obviously decreased. Thus, the amounts of H2O2 and
H3BO3 used for ecient incorporation of B and Ti into the
In the epoxidation of styrene, TS-2 has slightly higher
oxidation activity and selectivity for rearrangement to
phenylacetaldehyde than TBS-2, which is due to a higher Ti
content in TS-2. The catalytic activity of TBS-2 increases
with an increase in its framework Ti content, and the
selectivity decreases with an increase in its framework B
content. The products comprise 70±80% phenylacetalde-
hyde, arising from the Lewis acid±catalysed rearrangement
of the epoxide,9 20±28% benzaldehyde and formaldehyde
and about 1.5% phenylethanol, in agreement with the
results of Xia et al.10 In order to verify the formation
of PhCHO and HCHO, phosphoric acid was added to
the epoxidation reaction system. There was obviously an
increase in the formation of PhCHO and HCHO. Thus, we
Table 1 Results of XRD, IR and NH3-TPD for TBS-2 zeolites
TBS-2 Samples
XRD resultsa
Framework IR band intensityb
NH3-TPD
1
1
1
No.
x
y
z
V/A3
550 cm
960 cm
1380 cm
Tm/K
NH3 uptake
1
2
3
4
5
6
7
0.0
0.0
0.0
0.0
0.0
0.2
0.1
0.0
0.0
0.0
0.050
0.050
0.050
0.075
0.100
0.075
0.075
0.000
0.050
0.000
0.26
0.13
0.08
0.10
0.12
0.12
0.12
0.10
0.00
0.00
5343.2
5352.1
5349.5
5333.7
5314.6
5212.6
5239.5
5448.7
5214.1
5384.0
2.12
2.40
2.19
2.06
2.06
2.22
2.31
2.20
2.62
2.60
0.59
0.77
0.75
0.78
0.49
0.64
0.55
1.03
Ð
0.02
0.17
0.17
0.20
0.17
0.44
0.25
Ð
468
486
489
489
485
491
483
465
491
Ð
0.15
0.37
0.36
0.41
0.26
0.47
0.36
0.30
0.12
Ð
TS-2
BS-2
S-2
0.32
Ð
Ð
aMeasured by a Siemens D-500 diffractometer with Cu-Kꢀ radiation (ꢁ ˆ 1.54051 A). bMeasured by a Nicolt 510P FT-IR spectrometer;
1
band intensity (cm)/800 cm band intensity (cm).
propose that their formation is due to the catalysis of
Brùnsted acid sites produced by the co-ordination of H2O/
*To receive any correspondence (e-mail: yindh@hunnu.edu.cn).
$This is a Short Paper as de®ned in the Instructions for Authors,
Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is there-
fore no corresponding material in J. Chem. Research (M).
H2O2 to the Ti and B atoms of TBS-2.11 In catalytic re-
arrangement of styrene oxide, TBS-2 is obviously more

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J. CHEM. RESEARCH (S), 1998 765
Table 2 Results of epoxidation of styrene and rearrangement of styrene oxide over TBS-2 zeolites
Contents
Si:Ti
Epoxidation of styrenea
Rearrangement of styrene oxideb
Sample
SiO2:B2O3
Conv. (mol%)
PhCH2CHO Sel. (%)
Conv. (mol%)
PhCH2CHO Sel. (%)
BS-2
Ð
66.7
546.7
85.3
125.6
106.5
Ð
0
7.1
7.4
8.2
Ð
37.6
46.3
72.8
91.4
99.3
56.2
99.5d
96.2
98.3
97.9
98.5
99.2
96.8
79.6d
TBS-2(1)
TBS-2(7)
TBS-2(3)
TBS-2(4)
TS-2
78.9
75.8
62.1
58.4
45.2
58.4
78.0
70.9
75.4
72.1
78.2
51.6c
8.9
10.7
TBS-2(4)
106.5
12.1c
aStyrene (2.08 g), 30% aq. H2O2 (2.28 g), acetone (10 ml), catalyst (0.2 g), reaction temperature 333 K and time 5 h. Besides
phenylacetaldehyde, 20±28% benzaldehyde and formaldehyde, and 1.5% phenylethanol were obtained. bStyrene oxide (1 ml), acetone
(7 ml), catalyst (0.1 g), reaction temperature 333 K and time 5 h. Besides phenylacetaldehyde, a small amount of benzaldehyde (E3.8%)
was obtained. c48.4% Benzaldehyde and formaldehyde were obtained by adding 0.25 ml of 85% aq. phosphoric acid to the epoxidation
reaction system. d20.4% Benzaldehyde and formaldehyde were obtained by adding 1.14 g of 30% aq. H2O2 to the rearrangement
reaction system.
active and slightly more selective than TS-2, which is attrib-
uted to the greater number and stronger Lewis acid sites in
TBS-2.
We thank the Chinese government for their ®nancial
support by the National Natural Sciences Foundation of
China (29773013).
Experimental
Received, 24th June 1998; Accepted, 12th August 1998
Paper E/8/04836C
The synthesis of TBS-2 was as follows: titanium tetrabutoxide
(0.172 g) was added to water (5.0 g), giving a white precipitate
(hydrous titanium oxide). 30% aq. H2O2 was added to dissolve
the oxide (solution 1). Solution 2 was prepared from 11.6 g of 10%
aq. TBAOH and 10% aq. TMAOH was added to TEOS (4.76 g).
A solution containing boric acid in water (10 g) was then added to
solution 2. Stirring of 2 was maintained at 353 K for 2 h. Finally,
solution 1 was added dropwise to solution 2. The molar compo-
sition of the reaction mixture was 0.2 TBAOH±xTMAOH±1.0SiO2±
0.02TiO2±yB2O3±zH2O2±50H2O. The crystallization was done stati-
cally at 448 K for 4 d. The solid obtained was ®ltered o€, washed
with water, dried at 393 K for 2 h, and calcined at 813 K for 16 h in
air.
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1
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