Chemistry Reference
In-Depth Information
d
n
9
r
4
n
g
|
8
Figure 8.7 CeO
2
nanofibers used for HCl oxidation reaction, before (A) and after (B)
reaction.
135
A reaction mixture of HCl/O
2
/Ar
¼
2/2/3 at a flow rate of
15 mL min
1
(STP) at T
¼
703 K for 3 h on stream was used.
.
oxychlorides. The degradation of CeO
2
does not change the BET surface area,
as determined by nitrogen physisorption measurements (T
¼
77 K) performed
on the material before and after the reaction (S
BET
¼
40 m
2
g
1
). These results
are consistent with recently reported ones for the HCl oxidation over CeO
2
powder catalyst.
127
In addition to HCl oxidation experiments with pure CeO
2
nanofiber
catalysts, mixed CeO
2
-ZrO
2
fibers were also investigated (cf. Figure 8.8). For
the synthesis of mixed CeO
2
-ZrO
2
fibers, CeCl
3
7H
2
O and ZrOCl
2
8H
2
O
were mixed and then processed analogously as for the pure CeO
2
material.
The final mat of Zr
0.2
Ce
0.8
O
2
fibers exhibits pale yellow color. The mixed
oxide fibers consist of nanograins (typically 5-28 nm in diameter as deter-
mined by Debye-Scherrer equation).
Detailed experiments show that Zr
1
x
Ce
x
O
2
d
fibers are more robust
against chemical corrosion than CeO
2
fibers.
135
From Figure 8.8 it can be seen
that the morphology of the Zr
0.20
Ce
0.80
O
2
nanofibers does not change upon
HCl oxidation reaction. This conclusion is supported by XRD as no CeCl
3
,
hydrous or otherwise, shows up as reflections in the XRD data. The
Zr
0.20
Ce
0.80
O
2
nanofibers form a single cubic/tetragonal solid solution and
this structure is not affected by the HCl oxidation reaction. In comparison
with the pure CeO
2
nanofibers,
the nanograins of Zr
0.20
Ce
0.80
O
2
are
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