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Table 3 Effect of various oxidants on catalytic activity of CeZrO4ꢀd for which was conrmed by HRTEM and XRD. The uorite
ODH of EB
CeZrO4 catalyst shows better catalytic activity among the
ꢀd
catalysts studied for this particular reaction.
Selectivity%
Conversion%
(EB)
Yield%
(ST)
d
e
f
g
Oxidant
Nil
ST BZ TU SO CO
x
Acknowledgements
23
51
33
94
92
91
97
4.0 2.0
—
—
22
a
TR and KP thanks to SERB-DST (SR/S1/PC-17/2011) for funding.
Oxygen
4.8 1.0 0.4 0.8 47
2.0 1.0 5.0 1.0 31
b
Air
c
Carbon dioxide 07
2.0 0.6
—
0.4
7
Notes and references
a
ꢀ1
b
ꢀ1
GHSV 2400 h with respect to oxygen. GHSV 10 800 h with respect
c
ꢀ1
1
R. R. Miller, R. Newhook and A. Poole, Crit. Rev. Toxicol.,
1994, 24, S1–S10.
to air. GHSV 2400 h
with respect to carbon dioxide (reaction
ꢁ
ꢀ1
conditions: temperature 550 C, LHSV 3 h with respect to EB, 1
d
e
f
atmosphere pressure, 1 mL catalyst). ST-styrene. BZ-benzene. TU-
toluene. SO-styrene oxide.
g
2 E. H. Lee, Catal. Rev., 1974, 8, 285–305.
3
4
5
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ODH of EB was studied with so oxidants like CO
continuously in time on stream. EB conversion and ST yield for
CO as oxidant were low compared to other oxidants; it may be
due to coke formation or inability to activate the CO . There is
2
and air
2
2
492.
not much replenishing of lattice oxygen by air, so air as oxidant
shows less conversion than oxygen. If oxygen is used as an
oxidant, replenishing of the lattice oxygen by molecular oxygen
leads to enhancement in the catalytic activity which leads to
maximum conversion and selectivity. Maximum EB conversion
was obtained for oxygen as an oxidant. Table 3 shows the
effect of various oxidants on catalytic activity of CeZrO4ꢀd for
ODH of EB.
6
7
8
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9
Stable conversion and yield were obtained without oxidant
upto 15 hours. Aer that oxygen was introduced as oxidant,
conversion and yield attained maximum. Without oxidant, the
conversion was only 23% which might be possibly due to
minimum availability of lattice oxygen. If oxygen is introduced
into reaction, conversion suddenly increases to 40% this may be
ease of availability and replenishment of lattice oxygen. This
catalyst shows stable conversion and yield with different
oxidants up to 76 hours.
2
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1
1
1
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1
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CeO
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2
,
ZrO
2
,
CeZrO4ꢀd and PH-CeO
2
/ZrO
2
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Catal. Lett., 2009, 133, 307–313.
4ꢀd
maximum conversion of 50% towards EB and selectivity of 93%
towards styrene. Other catalysts (CeO , ZrO and PH-CeO /ZrO
show less catalytic activity compared to uorite CeZrO4ꢀd cata-
948.
2
2
2
2
)
20 E. Aneggi, C. de Leitenburg, G. Dolcetti and A. Trovarelli,
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+
3
+4
Presence of Ce and Ce oxidation states and oxygen vacancies
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by the XPS experiment. Fluorite CeZrO4ꢀd catalyst was stable up 23 S. N. Achary, S. K. Sali, N. K. Kulkarni, P. S. R. Krishna,
to 72 hours time on stream at optimized reaction conditions,
A. B. Shinde and A. K. Tyagi, Chem. Mater., 2009, 21, 5848–
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5859.
selectivity. The morphology and the structure of the uorite 24 I. Atribak, A. Bueno-Lopez, A. Garcia-Garcia and B. Azambre,
CeZrO4ꢀd catalyst were unchanged aer 72 hours reaction
Phys. Chem. Chem. Phys., 2010, 12, 13770–13779.
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