In conclusion, we have reported on a novel Ag@SiNW
catalyst prepared by an in situ EMD method, followed by
calcination. The SiNW arrays on the final catalyst can well
stabilize the in situ formed silver microparticles. This method is
promising for future research and utilization as a new ap-
proach for catalyst preparation because of its effectiveness,
facility, low cost and reproducibility for mass production. This
catalyst shows high thermal stability at high temperature
owing to its special ‘‘rocks-in-forest’’ structure, and exhibits
excellent activity/selectivity in the gas-phase selective oxida-
tion of 1-octanol. These results highlight the great potential of
Ag@SiNW catalyst in the selective oxidation of high alcohols.
Furthermore, based on the idea proposed here, a series of
novel catalysts could be developed by embedding the active
species into open-structured nanowire arrays as needed. Re-
search on further designing efficient catalytic systems based on
the utilization of SiNW arrays as the support is being carried
out in our laboratory.
Scheme 2 Selective oxidation of 1-octanol over silver-based catalysts
to its corresponding aldehyde.
Table 1 Conversion and product distribution of 1-octanol oxidation
over Ag@SiNW and electrolytic silver catalysts
a
Selectivity (mol%)
b
Catalyst
T/
Conversion 1-
(%) Octanal
Octanoic C. & O.
acid
1C
Ag@SiNW
300 65.2
96.2
96.1
90.8
3.2
2.2
1.5
0.6
1.7
7.7
3
4
50 90.0
00 95.5
Electrolytic
Ag
300 72.2
70.3
3.3
26.4
3
4
50 90.7
00 97.7
68.6
47.6
2.3
1.6
29.1
50.8
c
Ag–Si
300 41.6
84.2
71.0
65.3
1.8
0.8
0.5
14.0
28.2
34.2
This work is supported by the NSFC (20673026, 20721063),
STCMS (06DJ14006, 075211013), and the Major State Basic
Research Development Program (2003CB615807).
3
4
50 53.9
00 62.4
SiNWs
400 2.1
—
—
—
a
A continuous fixed bed reactor system was adopted; pressure =
À1
Notes and references
1
9
.0 atm; O
2
/alcohol = 1.0; air flow = 70 ml min (STP); N
À1
2
flow =
0 ml min (STP); amount of alcohol inlet = 6 ml h ; weight of
À1
1. Y. Okinaka and T. Osaka, Electroless Deposition Processes:
Fundamentals and Applications, VCH, Weinheim, 1990.
b
catalyst = 0.6 g. C. & O. = cracking and over oxidation products.
c
The sample was prepared by mixing electrolytic Ag and Si powder
mechanically with 36 wt% Ag.
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The target product of this reaction is 1-octanal, which is a food
flavor with a fruit-like odor and also an important intermedi-
ate of organic synthesis for other fragrances, such as a-hexyl
cinnamaldehyde, 2-heptyl-1,3-dioxolane and 4-methyl-2-hep-
tyl-1,3-dioxolane.
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Table 1 displays the relationship between the conversion/
selectivity of 1-octanol oxidation and reaction temperature
over Ag@SiNW and a commercial electrolytic silver catalyst.
In the temperature range from 300 to 400 1C, SiNWs after
removing Ag species are almost catalytically inert to this
reaction as shown in Table 1. It is worth noticing that
Ag@SiNW presents a much higher selectivity to the target
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same LHSV and temperature. As shown in Table 1, the
activity of Ag@SiNW was much higher than that of Ag–Si
due to its open micro-environment and stable Ag microspheres
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